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1. lt 9 gt 0 1 0 1 1 0 10 0 Period s Fig 5 SPZ Calibration curve January 1985 Record 1986 12 24 09 239 000 e 100 c 2 o Cx 2 10 100 Period s Fig 6 LPZ Calibration curve January 1985 Record 1986 12 24 09 240 LA Waw SPN SPZ COUR RECORDER LPZ SPE 3 1 3638 Hour Minute TO Minute 4 Radio pips N 1N484I puc iuc Id Min GROUND FROM DUAE Haut GED CLOCK Bi CLOSURE TO PS GROUND FROM RADIO RELAY 6 Hour CLOSURE TO 10 Sec GROUND FROM isse GED CLOCK CRO EE IG Tantalum O t TRIGGER MONITOR NOISE PULSE REDUCING E CAPACITORS 4 7 Be 38 4 7K 22K 25K I2V BROWN Pin 18 Supply RADIO CLOSURE ORANGE 17 Ground Q YELLOW 14 12 BLUE 9 58 E 6 6H EXTERNAL RIBBON CABLE TO EN SUPPLY GED CLOCK 581926 PURPLE 5 Hour e C BLUE 4 Mi 2 GREY 3 Min WHITE 2 Id Sec WHITE iSec END BANANA SOCKETS TO RELAYS MONITOR O pELAY ADJUS SIDE VIEW circuit Fig 7 Time mark relay driver box Record 1986 12 SIDE VIEW 24 09 242 1 PLUS POSITION 3 MINUS POSITION 6 ZERO POSITION Fig 8 QHM odd pi mode geometry Record 1986 12 24 09 244 Pelersen sland Rouse S Ds
2. ae es de nS X 4 00 Calibrations eS we a GK ico U 1 XV 5 CONTROL EQUIPMENT Power um See sas edm Axe Bos dq x rs 6 BUILDINGS AND BUILDING MAINTENANCE 7 OTHER DUTIES ACKNOWLEDGEMENTS REFERENCES Contents APPENDIX HISTORY OF INSIRUMENTATIOM UP TO 1985 APPENDIX 8 P P PEN N PAPER PARAMETERS APPENDIX C FUTURE PROCESSING OF PEM DATA APPENDIX D 5 AND VARIOMETER CONTROL APPENDIX E USING THE QHM IN ODD PI MODE APPENDIX F EAST BAY ICEFALL JULY 1984 TABLES O N Doh G9 9 WPF amp FIGURES O CO N OD O1 WP Contents STATION DATA FOR MAWSON 1984 RESULTS OF ORIENTATION TESTS La Cour MAGNETOGRAPH SCALE VALUE AND ORIENTATION COIL CONSTANTS 1984 INTERCOMPARISONS OF MAGNETOMETERS Mawson February 1984 INTERCOMPARISONS OF MAGNETOMETERS Mawson February 1985 OBSERVED BASELINE VALUES FOR LA COUR MAGNETOGRAPH 1984 QHM RESIDUAL TORSION CORRECTIONS at Mawson LA COUR MAGNETOGRAPH PARAMETERS 1984 PRELIMINARY INSTRUMENT CORRECTIONS 1984 PRELIMINARY MEAN MONTHLY AND K INDEX VALUES 1984 5 GEOMAGNETIC ANNUAL MEAN VALUES 1974 1984 AND La Cour COMPARISON INTERCOMPARISONS OF MAGNETOMETERS Davis January 1984 INTERCOMPARISONS OF MAGNETOMETERS Casey March 1985 HORIZONTAL SEISMOGRAPH PARAMETERS
3. overfixation of the photographic records faint or off scale traces during active magnetic storms adjustments to the variometers magnetic interference from quarry vehicles 10 variometer malfunction caused by blasts Upon the author s arrival the following problems with the magnetograph existed 1 there was no D timemark trace Marks 1982 2 the 7 trace was almost at the limit of its adjustment 3 D and Z reserve traces were either absent or out of adjustment Following the failed attempts to rectify the D timemark and reserve trace problem by Silberstein and Cechet no further attempts were made until the D and baselines were adjusted However this attempt was also unsuccessful The D trace was adjusted up the record on November 19th when data losses during large magnetic storms began to occur The H trace was considered to be acceptable and no adjustments were made to it throughout the year Mawson Magnetic Observatory 2 2 7 trace eventually drifted upwards to the top of the record until data began to be lost during magnetic storms November 19th the 2 traces were adjusted down the record Some baseline changes of unknown origin occurred during the year not always to all traces at the same time Some possible reasons are the deposition of magnetic building materials the proximity of the variometer building occasions vibrations from machinery and quarry blasts
4. electronics were set up according to the manual only problem encountered arose from the photographic safelight positioned above the Y unit Contrary to the 1983 report Cechet 1984 safelights do interfere with the operation of the PEM The orientation of the X unit was carried out using theodolite orientation of the theodolite was determined from the standard wall markings and the orientation coils were aligned using the theodolite telescope Difficulties were encountered because the floor of the building was not sufficiently rigid base for the theodolite and the depth of focus of the theodolite was shallow less than the diameter of the coils The unit was very easily moved when replacing the thermal covers due to the bulk of the cover and the small clearance around the PEM necessitated by small piers The thermal covers were slightly modified to help avoid the problem in future The installation of the Y PEM was slightly different to the method described in early versions of the PEM manual and to the method used by Cechet The orientation coils were assumed to be aligned true East West from the previous installation this may not however have been the case as Cechet used a different installation technique After the majority of the procedure recommended in the manual had been followed the orientation the QHM magnet was adjusted moving the position of the photodiode until the application of a large
5. 1486 12 2 BUREAU OF MINERAL RESOURCES GEOLOGY AND GEOPH YSICS RECORD RECORD 1986 12 MAWSON GEOPHYSICAL OBSERVATORY ANNUAL REPORT 1984 BY Peter CROSTHWAITE The information contained this report has been obtained by the Bureau of Mineral Resources Geology and Geophysics as part of the policy of the Australian Government to assist in the exploration and development of mineral resources It may not be published in any form or used in a company prospectus or statement without the permission in writing of the Director 28601201 SUMMARY 1 INTRODUCTION 2 MAWSON MAGNETIC OBSERVATORY 2 l Absolute Instruments BR 2 2 Cour Ma gnetograph loud de Ae bow ge DESDE QE cO 2 3 Photo electric Magnetograph 2 4 Comparison of La Cour PEM Data 49 Temperature Ae 2 6 Surveyed Reference m On 2 7 Comparisons for QHM302 as a field declinometer CommuniCal TOS 3G amp ac 3 OTHER ANTARCTIC OBSERVATORIES Sl Danis Os d Y dE 3 2 ERE ue Eh OE 3 3 Macquarie Island WTCC 3 4 Remote Automatic ODSEVVALOV IGS 4 SEISMOLOGICAL OBSERVATORY Hel pera 1111 0 we 9
6. he analysis procedure was as follows make a data file of all the QHM and declinometer results with the corresponding EDAS values of X and Y and the value of the Doric temperature 2 exclude any individual QHM observation which disagrees with the other QHM observations in the same set Mawson Magnetic Observatory 3 use the average declination and horizontal field strength during a set of observations taking into account the field variation in all calculations 4 make the initial assumption that qx and can be calculated from the constants of the QHMs in the PEMs see Appendix B and that and sy are as measured by scale value tests throughout the year and that ex ey Rx Ry are zero 5 determine graphically the initial estimates of Rx Ry Dx and Dy 6 determine graphically the values of ex and ey 7 redetermine using linear regression analysis better values for qx and 8 redetermine the values of Rx Ry Dx and Dy by the following method i assuming a reasonable asymptotic baseline perform a regression analysis of LOG deviation from the asymptotic baseline vs time ii repeat step i for a range of baselines either side of the estimated asymptotic baseline iii choose the baseline and associated constants which give the best correlation result in the step ii 9 redetermine sx and sy using regression analysis 10 redetermine ex and ey using regression analysis 11 repeat as many steps as
7. During a plus odd pi rotation the QHM head rotates through m pi phi and the magnet rotates through phis Hence the twist developed in the fibre is m pi phit phi During a minus odd rotation the head rotates through m pi phi and the QHM magnet rotates through phi Hence the twist developed in the fibre is m pi phi phi m pi e See Figure 8 for some help in visualising the geometry of the situation So the equations of equilibrium in the zero n pi and n pi positions become M H sin a M H sin phi a T B m pi M H sin phi T B m pi 4 e and so M H sin phi a sin phi a 221 2 M H 2 1 Appendices E 1 sin phi a 2 m pi T 74 From 2 M H sin phi cos b m pi T i e m T pi M sin phi cos b K m 1 kl t 1 cos b TE 19 where b phi phi 2 which is very much like the standard QHM formula fact it is the same only difference is that phi and phi are not directly measureable angles Only 1 and 1 are directly measurable So it is only reasonable to express b in terms of these quantities Thus e phi 2 4 and e must be determined This can be done by comparing even pi and odd pi observations From equation 1 M H
8. Temperature coefficients for the and variometers were determined by a least squares analysis of baseline vs temperature data results for were very speculative due to a large scatter in the data However it is fairly certain that the temperature coefficients for the La Cour are quite small but not negligible See Table 8 2 2 4 Temperature baseline and scale values temperature of the H and 7 variometer thermometers was read every chart change and before and after every set of absolute observations These measurements were related to scalings on the magnetograms a least squares analysis was used to determine the temperature scale values adopted scale value was then used to determine baselines See Tables 6 and 8 2 2 5 Data Although the author was present from February 1984 until March 1985 only the data from February 1984 until January 1985 inclusive was processed Discontinuities in the La Cour baselines and possible scale value changes to the 4 variometer during January 1985 accompanied by a change in absolute observation procedure in February 1985 i e the reintroduction a PPM to measure and hence determine 7 baselines the abbreviation of the measurement of by excluding QHMs 301 and 302 from normal observations made it appropriate for the data to be considered with the remainder of the 1985 data apology to my successor for the apparent shunning of responsib
9. rearrangement magnetic materials in the rock crusher quarry site Other baseline changes were caused directly from quarry blasts less than 100 meters from the variometer building blast dislodged the Balance de Godhaven magnet and affected 7 measurements for over week until all of the associated problems were rectified 7 trace appeared almost normal even when the magnet was not resting its agate however baseline reductions and scale value observations were very scattered Replacing the magnet failed to solve the problem until the magnet and agate were thoroughly cleaned It is suspected that the end result of the incident was to change the scale value of the 7 variometer Continuing observations by the 1985 geophysicist will be required to confirm this Other results of blasting included vibrating some of the very old wiring in the variometer hut to the point where a few critical connections broke and some timing relay driver circuits failed Such problems were always very time consuming to fix as there were virtually no wiring diagrams of the 014 system left and many modifications had been made in an ad hoc undocumented fashion The relay drivers in the variometer side of the timing circuitry caused many problems relay chatter transistor failures etc hey were eventually removed from the system and replaced by a reliable wire shunt Apparently they had been installed when the Science Building end of the ci
10. 18 1 a dH H kl dt 1 kl t 1 tan a 1 tan a B n pi B 9 Substituting for dB from 4 into 8 dp tan phi 0 kl dt 1 kl t 1 tan a 1 tan a B n pi B 10 J From 3 5 and 7 sin a B 51 1 a 4n pi B sin phi a n pi B T M H From the standard formula for QHM calculation T M H K H pi This quantity is typically of the order 0 1 and at most it may be 0 32 i e 1 81 Equations 4 9 and 10 be therefore approximated very roughly in the case of 4 to dp tan p dH H kl dt 1 1 for whatever value of p is relevant If the actual circle reading c is now considered then dc dD dp where D is the declination Hence the effect of field changes on the circle readings can finally be written as dc dD tan p dH H kl dt 1 kl t Substituting dD sin D H dX cos D H dY and cos D dX 51 0 dY and remembering to take into account the unit of angle is the radian Appendices D 3 for zero readings dc tan a kl dt tan a cos D sin D dX H tan a sin D cos D dY H for plus readings dc tan phi a kl dt tan phi a cos D sin D dX H 1 18 1 a sin D sin D dX H for minus readings dc tan phi a kl dt tan phi a cos D sin D dX H tan phi
11. 5 2 3 Programming Unit TMU 1 TMU was used until the 1985 changeover It gave few problems during the year other than 1 occasional minute jumps from static or while altering the instrument rack wiring 2 twice when the unit failed 8 it worked again when it was reset 3 an occassion when it completely lost track of the time he TMU is antiquated and there is little need for it now 1 will no longer be used once the La Cour is withdrawn from service 5 2 4 PEM Linseis Clock This cheap and nasty little clock was used to provide hour marks the Linseis chart recorder for the PEM analogue system It suffered from static Control Equipment 5 3 related time increments and failed to provide any timemarks from 2000 to 2359 It is due to be made redundant by the GED clock which can directly drive a W amp W recorder but not a Linseis and retired This clock annotated the analogue charts via multichannel split output relay box the digital recorder was not sent time mark signals t 5 3 Cables The following cables were superseded and removed the pyrotenax cable from the Cosray building to the Science Building 2 the multi core shielded cable from the Cosray building to the Science Building 3 the multi core shielded cable from the Old Seismic Vault to Science Building 4 a variety of cables originating in the office magnetic and seismic buildings and leading no
12. Many problems then occurred and no problems principally noise problems were solved particular there was an interaction between the and SPZ systems causing for example the SPZ calibration pulse responses to be superimposed on the LPZ record There was no suitable Cannon plug available to tap the calibration output from the rack and ad hoc alligator clips had to be used The systems were found to be wired differently the rack wiring used the LOW gain output form the 5 while the ad hoc wiring used the HIGH gain output detailed rack wiring diagram was not to be found and although it appeared that the seismometers and seismometer to 5 cable shields were not connected to the appropriate 5 pins problems with the rack could not be located without shutting down the seismic system and rebuilding the circuit Rather than doing this the LPZ amplifier was returned to the top of the baked bean box from whence it came and a combined SPZ LPZ SPN and SPE circuit rack or parts was ordered for the following year Unfortunately it was never supplied the unsatisfactory arrangement persisted at the author s departure The vertical seismometer system suffered many problems most of which are described in earlier reports A high frequency noise problem which was expected to be solved the installation of new shielded multi twisted pair cable and balanced AR 320 helicorder amplifiers persisted Th
13. in the apparent height of the bergs and cliffs average height of the bergs was estimated to be 70 of the maximum height for the major bergs The height of the remaining icecliffs were 3m to 50m The size and location of the bergs were measured by the angles subtended by them at the Cosray Building using a theodolite and Petersen Island using a sextant and their angular displacement from Welch Island and the trig station on Rouse Islands from the same locations The locations of the bergs may seem odd when related to the Mawson map but the shape of the coast has changed considerably since the map was made Appendices F 1 1 STATION DATA FOR MAWSON 1984 Magnetic Absolute Hut Pier A instrument level Geographic coordinates 067 36 14 2 S 62 52 45 4 E Geomagnetic coordinates 73 15 102 9 E as stated in previous reports Geomagnetic coordinates 73 345 105 86E from IGRF 1980 pole 78 805 109 24E Geomagnetic coordinates 73 355 106 44E from IGRF 1980 extrapolated to 1984 pole 78 91S 109 03E Elevation m 12 Foundation Precambrian Granite Magnetic Variometer Building NEW Mark NI Geographic coordinates 07 36 11 4 S5 62 52 44 5 E Elevation m 09 Foundation Precambrian Granite Magnetic Variometer Building OLD Geographic coordinates 67 36 13 0 5 62 52 38 5 E Foundation Precambrian Granite Cosray building Seismometer platform Geographic coordinates 67 36 16 6 5 62 52716 6 Elevation
14. Average Maximum HTM 570704 7 3 1 12 0 nT 174 1 nl 4 1 1 QHM 300 1 6 nT 3 5 DEC 640505 0 2 0 8 DEC 630332 0 3 0 5 The results quoted for the HIM 704 QHM 300 comparisons Cechet 1984 are incorrect Tables 5 INTERCOMPARISONS OF MAGNETOMETERS Mawson February 1985 Date Instrument A Instrument B Difference A B at 18500 nT Feb 13 16 85 HTM 570704 QHM 300 3 9 1 3 0 00021H Feb 13 16 85 172 QHM 300 40 9 0 8 nT 0 00221H Feb 15 16 85 Dec 640505 Dec 630332 0 4 4 0 3 Cir 508813 Cir 611665 Feb 21 85 Geometrics 816 MNS2 2 9 2 3 1 nf The values of the residual torsion deviation alpha for these observations were HTM 704 1 1 1 0 172 5 3 0 5 QHM 300 3 0 0 8 Values are given with no instrument corrections applied PEM EDAS data were used to calculate delta H and delta D reduce all H comparisons and all D comparisons to a common time for each set Four sets of H comparisons HTM704 QHM172 QHM300 QHM300 QHMI72 HTM704 were made Four sets of D comparisons 640505 630332 630332 640505 were made comparisons were performed alternating measurements Pier until the average instrument difference ceased to vary appreciably 15 pairs of F measurements were made Declination observations were made in the proper way see Feb 84 comparison comments Through routine baseline determinations from Fe
15. a sin D cos D dY H Not all of the terms relevant all of the time Taking an extreme case with phi 60 dt 2 C dH 50nT 8000nT 3 with 00005 tan phi dH H is about 35 tan a dH H ues 1 kl tan phi dt 0 6 kl tan a dt 20 2 In this example the calculated value of varies by about for a variation in phi of 1 temperature correction for the zero readings is not therefore very significant and the H correction for the zero reading is required only for a very badly adjusted QHM The quiet ing coefficients could be calculated accurately enough assuming that 0 and phi phi are an average value for phi for most cases However if computers are going to do all of the work then why bother approximating anyway The above technique was applied to a very limited set of observations from Macquarie Island The observations were not made in such a manner that the circle readings coincided with the midpcint of the EDAS sampling interval so the variometer corrections were not as good as they could have been The and D values derived from the observations processed this manner were compared to the values derived from the usual processing after being reduced to the same point in time by averaging the four EDAS ouputs at the and readings for the observation and calculating the relevant delta H and by averaging the two EDAS out
16. cf Cechet s result 274 14 4 The brass peg actually subtends a significant angle from the pier and so surveyed angles may vary a little It is also tall and a little bent There is no definite point the peg to refer to The mark is now obscured from view from the pier by the New Variometer building mark SOH is near the quarry site and with future extensions to the quarry planned it is in danger of being damaged or destroyed new declination reference mark engraved BMR 1985 2 was installed as a backup mark following the loss of the brass peg It is a hexagonal brass rod extending some 15cm from the ground south southwest of the pier It is coloured with blue and yellow tinted epoxy and conical at the top to provide a definite reference mark top of the peg is also turned with a raised centre so that theodolite can be exactly positioned over the reference mark Hence the mark can be used as sunshot station It is suggested that sunshots from the mark be used to determine its azimuth from Pier A in the near future Its approximate azimuth determined by measuring the angle between SOH and 1985 2 from Pier is 241 03 7 2 7 Comparisons for QHM302 as a field declinometer In preparation for expected opportunity to measure the field at Scullin Monolith comparisons between QHM302 circle 49 the field declinometer Askania declinometer 630332 circle 611665 and QHM300 were carried out on the 15
17. lt Jocelyn 2 Islands Teyssier island Limits of effects on ice sheet Limits of scattered sea ice and ice debris MAWSON e Bn Location of the four major icebergs Fig 9 East Bay icefall map Record 1986 12 24 09 245 d C Nl Jn DAT m em seat e T 41 4 D 3X E E A ji MW LET u D ar 4 X y i 1 t 7 1 1 M vl M Fit aM i i gu ditate elt T Y i T fi 4 rT 1 4 NA i usc d N oA mae r lt 7 TI a E at M 6 j E Ed iU AT a Record 1986 12 Fig lO East Bay icefall seismograph IO July 1984 rc Fan EAST pu a ugs 47 wt y 89 u a me vn TERN a PART s ety i a n Heal
18. then corrections that need to be applied to the data would be as obvious as they are important eg orientation errors in the PEM alignment It is a fact of life that at the extremes of the data the field is very active and at such a level of activity very good variometer control of the observations is essential to reduce the baseline reduction scatter enough to determine the corrections For this reason a high display rate is desirable during absolutes There are two ways of improving the system 1 A cheap way The EDAS could be reprogrammed to collect data at a fast rate say every 10 seconds or faster and to display and record at different rates The recording could then carry on as ususal and the display could occur at a much higher rate during calibrations scale values and absolutes and at a much lower rate all the time to print out mean hourly ordinates This would eliminate all analogue scaling allow more accurate preliminary data to be produced at the observatory greatly improve the results calibrations and provide the mean hourly ordinates as backup to the full digital recording 2 expensive way Install a programmable micro or minicomputer to record the data multi tasking system could concurrently acquire and record data at any rate and display or process current or noncurrent data absolutes etc and be used as a general data analysis graphics report writing tool This would improve the quality of t
19. 0 46424 49955 4 0 5 8 April 18448 63 32 3 46426 49957 3 8 3 9 May 18445 63 31 5 46412 49943 3 8 3 8 June 18436 63 33 8 46410 49938 3 8 4 8 July 18430 63 34 4 46393 49920 4 13 8 August 1845 63 34 2 46386 49921 3 8 4 September 18443 63 35 1 46390 49922 4 1 3 8 October 18450 63 35 6 46388 49922 4 0 3 7 November 18458 63 34 4 46387 49924 4 1 4 8 December 18458 63 35 0 46371 49910 4 2 4 8 1985 January 18466 63 35 0 46368 49910 3 8 3 7 Mean 1984 18446 63 33 1 46404 49936 4 0 Feb84 Jan85 18448 63 33 5 46399 49932 4 0 F values are derived from H and 7 data PPM measurements were made Tables 11 GEOMAGNETIC ANNUAL MEAN VALUES 1974 1984 DW 1 Y Z7 F oi i f nT nT nT nT nT 1974 62 24 8 68 47 2 18390 8516 16298 47380 50824 1975 62 31 4 68 44 0 18397 8488 16321 47269 50723 1976 62 37 3 68 40 0 18418 8470 16354 47157 50626 1977 62 43 9 68 36 9 18525 8442 16376 47051 50530 1978 62 51 9 68 35 5 18421 8402 16392 46986 50468 1979 62 57 9 68 32 9 18425 8375 16411 46890 50380 1980 63 05 8 68 29 8 18432 8340 16436 46784 50284 1981 63 14 6 68 27 1 18443 8303 16467 46705 50215 1982 63 21 2 68 25 5 18433 8267 16475 46616 50128 1983 63 26 6 68 22 3 18439 8245 16493 46503 50025 1984 63 33 1 68 19 2 18446 8216 16515 46398 49930 Mean annual changes 1974 1984 6 8 2 8 5 6 30 0 21 7 98 2 89 4 1974 1979 6 6 2 9 7 0 28 2 22 6 98 0 88 8 197
20. 1983 May 1984 VERTICAL SEISMOGRAPH PARAMETERS pre February 1985 SEISMOGRAPH PARAMETERS post February 1985 SPZ SEISMOGRAPH CALIBRATION October 1984 SPZ SEISMOGRAPH CALIBRATION January 1985 LPZ SEISMOGRAPH CALIBRATION January 1985 TIME SERVICES FREQUENCIES PROPAGATION DELAYS Reference Marks and Azimuths Seismic Vault Layout SPH electronics rack wiring diagram SPZ Calibration Curve October 1984 SPZ Calibration Curve January 1985 LPZ Calibration Curve January 1985 Time mark relay driver box circuit QHM odd pi mode geometry East Bay Icefall Map East Bay Icefall Seismogram work described in this report was part of the BMR contribution to the 1984 Australian National Antarctic Research Expeditions at Mawson This contribution consisted of continuous recording of seismic activity and the geomagnetic field The geomagnetic field was recorded using a normal La Cour magnetograph recording H D and Z components photographically for the entire year In May a two component X and Y Photo electric Magnetometer PEM was connected toa digital recorder an EDAS unit utilizing a magnetic cassette drive and a visual multichannel chart recorder Seismic activity was recorded using a Benioff short period seismograph and a Press Ewing long period seimograph onto two hot pen helicorders In addition two Benioff short period horizontal seismometers recorded activity on a photographic drum recorder until the photo
21. 41 0 35 3 0 3 65 7 56 5 0 4 102 3 88 0 0 5 135 0 116 1 0 6 168 5 144 9 0 7 192 6 165 6 maximum 0 8 195 6 168 2 magnification 0 9 180 5 155 2 1 0 151 2 130 0 1 1 115 2 99 1 1 2 90 8 78 1 1 3 72 0 61 9 1 5 45 6 39 2 2 0 18 4 15 8 3 0 5 4 4 6 4 0 2 2 1 9 5 1 1 1 1 0 Magnifications are given at 5 set to 9696 gain Odb attenuation 0 1 10Hz passband AR320 24db attenuation Seismometer Free Period 0 96 secs Damping Resistor 386 ohms currents used 500 microamps approx p p value Weight lift tests 0 141 mm mg masses used 100mg Current pulse tests 18 6 mm mA currents used lmA 2mA Motor Constant 1 29 N A results of weight lift tests are certainly incorrect due to a certified 100mg mass used in the tests being other than its stamped mass results of the weight lift test are inconsistent with subsequent tests and the derived motor constant is similarly inconsistent first column of magnifications has been corrected by a factor of 1 29 1 50 the ratio of the derived motor constants in the calibrations in October 84 and January 85 to give the second column of magnifications Tables 19 5 7 SEISMOGRAPH CALIBRATION January 1985 Period secs 0 31 8 23 x 1000 0 41 11 1 0 51 16 5 0 62 19 6 0 72 20 1 0 82 21 5 0 93 18 5 1 02 15 4 1 12 11 8 1 19 9 88 1 31 7 28 1 53 4 53 2 03 1 88 3 03 0 56 4 08 0 22 5 10 0 11 Magnification maximum magnification Magnifications are gi
22. La Cour magnetograph was renamed sensitive magnetograph Smith 1971 15 mm hr normal recorder replaced 20 mm hr recorder Hill 1978 15 mm hr sensitive recorder replaced by 20 mm hr recorder MNS2 proton precession magnetometer installed for absolute measurements Sensitive recorder removed Photo electric magnetometer PEM X and Y components installed MNS2 1 Proton precession magnetometer ceased operation Digital recording of PEM X and Y component data began Seismological Three component Leet Blumberg seismograph Pen and ink recorder installed Three component seismograph installed consisting of Benioff Appendices A 1 Feb Sep Dec Apr Jul Mar Aug May Feb 1963 1970 1973 1977 1978 1981 1983 1983 1984 1985 seismometers free period 1 0 s and three channel single drum recorder galvanometer 0 2 s free period horizontal galvanometers free period 70 s Merrick 1961 recorder replaced by Benioff 60 mm min three channel recorder 14 s free veriod horizontal galvanometers installed Black 1965 14 s free period horizontal galvanbometers replaced by short period 0 2 s galvanometers Robertson 1972 2 seismometer transferred to vault beneath Cosray building Almond 1975 Transfer of Geophysics office including power and timing to Wombat Science Block D Recording of SP N Benioff seismometer discontinued Petkov
23. Scale Value Constant Orientation Constant nT m nT mA X 8 03 8 03 Y 8 03 8 03 H 8 07 8 07 D 8 07 8 07 Z 7 49 Tables 4 150 5 OF MAGNETOMETERS Mawson February 1984 Date Instrument A Instrument B Difference A B at 18500 19 23 84 570704 QHM 300 6 2 0 8 0 00034H 19 23 84 174 300 235 4 0 5 0 00191H Feb 15 16 84 640505 Dec 630332 0 9 0 3 Cir 508813 Cir 611665 The values of the residual torsion deviation alpha for these observations were HTM 704 0 8 2 0 174 15 5 1 2 QHM 300 5 1 0 Values are given with no instrument corrections applied Cour data were used to reduce all observations to baselines Four sets of H comparisons 704 QHMI74 QHM300 QHM300 QHM174 HTM704 were made Four sets of D comparisons 640505 630332 630332 640505 were made Declination observations were made using an improper procedure the declinometer base was left on the circle while siting the reference mark This will introduce a refraction error into the comparison results attempt was made to correct these results as the refraction error for 640505 508813 was not known As a quality check on observer performance variometer sensitivity and absolute instrument reliability one may note the following observation scatters Instrument Difference between observations in the SAME set
24. Unit were removed from circuit and replaced with a relay driver see Figure 7 which directly drove the seismic system and drove the magnetics via a single relay This was done to avoid the alternative of introducing a string of relays with multiple relay action delays into the timemark circuitry of the seismic system and to reduce the load on the GED timemark transistors Unfortunately the clock derived timemarks are not as clear as the TMU timemarks and occur only every 10 minutes with an emphasised mark every hour compared to the TMU marks every b minutes and also on the 59th and Olst minutes relay driver box contained a delayed triggering circuit to drive CRO and a second pulse output that could be monitored on the CRO to make time corrections clock was also used to synchronise the Advance Electronic Inverter This gave problems as the clock was not capable of driving the 50 ohm load at a sufficient voltage to synchronise the inverter Consequently an impedance buffer and transistor drive were connected to the 50Hz clock output The rate of the clock was carefully adjusted throughout the year so that the required 50ms accuracy was maintained during long periods of poor radio reception Most of the time it was kept within 5 ms day At one stage the clock hiccoughed and went from nice 1 ms day rate to a 100 ms day rate No reason was obvious and the clock eventually settled down again and resumed being nice
25. knowledge of alpha and the average asymetry of the n pi readings The results of the comparisons are listed in Table 14 It appears that the Casey observer was not properly briefed the importance of maintaining magnetically clean environment in the Absolute Hut and that there were no suitable non magnetic tools that could be used in repairing magnetometers Ordinary screw drivers etc were probably used instead possibly altering the magnetometer constants 3 3 Macquarie Island A brief examination in passing of the Maquarie Island observatory was made All equipment appeared to be working correctly the installation was impressively neat and tidy all personnel assisting BMR in running the observatory appeared keen and capable and it was a beautiful warm sunny day and the absence of any problems was much appreciated 3 4 Remote Automatic Observatories These observatories do not exist as yet but the power supplies and communications facilities of Automatic Weather Stations that have been deployed around Antarctica and other places by the Bureau of Meteorology could be used to provide otherwise unobtainable continuous recordings of the field from very remote locations The movement of icebound stations would be a source of baseline drift but it may be worthwhile looking into building gimbled Z D magnetometers which would have to be corrected for D during possible rotations of the magnetometer along with the surrounding ic
26. m 17 Foundation Precambrian Granite Old Seismic Vault location of SPH seismometers until May 1984 Geographic coordinates 67 36704 2 5 62 52 24 1 E Elevation m 08 Foundation Precambrian Granite The co ordinates of Pier A Mark and the Cosray building seismometer platform were measured by the author using ISTS 51 as a reference location This reference 1 a satellite trig station positioned by the road near the Old Seimic Vault and the Bureau of Meteorology buildings Its location is 67 36 04 95 S 62 52 23 66 E its height above mean sea level is 9 79m and its spheroidal height is 39 37m The co ordinates of all buildings were measured by Australian Survey Office surveyors and the WGS 72 co ordinates provided by ASO agree within 0 2 of latitude and longitude with the instrument pier co ordinates measured by the author Elevations quoted are Height Above Mean Sea Level The elevations of Pier A Mark and the top of the Cosray shaft were measured relative to ISTS 5 The quoted elevation of the seismometer platform assumes the shaft to be 13m deep elevation of the Old Seismometer Vault was taken from the 1983 Mawson report Tables 2 RESULTS OF ORIENTATION TESTS ON La Cour MAGNETOGRAPH Component Reference Magnet N Ex Orientation N Pole Date Field degrees H 18Sep84 18450 0 9 south D 18Sep84 63 34 0 West N 0 4 West Z 12Nov84 46388 nT N 2 3 Down 3 SCALE VALUE AND ORIENTATION COIL CONSTANTS 1984 Component
27. necessary to refine the data initial values chosen were qx 3 02 nT C 7 97 nI C 0 1974 nT count 5 0 2050 nT count After the analysis was complete the following values were accepted qx 3 15 nT Doric degree see Temperature Coefficients below 8 53 nT Doric degree see Temperature Coefficients below sx 0 1968 nT count sy 0 2065 nT count ex 0 0041 ey 0 051 Rx 19 nf Dx 250 days Ry 2 58 ni Dy 500 days It is questionable whether it was justifiable to adopt the above values of SX Sy ex and ey given the scatter in the data relative to the range in x y Y and X respectively particularly for the Y component Also quite a range of Rx Ry and Dy values can reduce the data to reasonable straight line Nevertheless the above procedure gives an objective way of choosing reasonable values The accepted constants give asymptotic baseline values of 7876 9 nT 1 4 nT for X 16090 2 nT 1 6 nT for Y To make these baselines comparable to the La Cour baselines in Table 6 it is necessary to apply D correction of 1 2 WEST for the error observation Mawson Magnetic Observatory 2 8 technique using the declinometer see Section 2 1 Absolute Instruments and correction of 1 3nT as the PEM processing used an average 300 301 302 value rather than just the QHM 300 value as in La Cour processing This corresponds to a correction o
28. of the event The following data was recorded The area south of Rouse Islands extending from the coast to Jocelyn Islands and Teyssier Island an area 1800m by 1500m was effected by upheaval and ridging of the plates of seaice along the perimeter between the islands area extending 800m out from the 1800m of coast was completely shattered by the movement of the icebergs breaking away from the icecliffs There was a water wave associated the fall the shores of Horseshoe Harbour were very broken up by the wave and pools of water were left behind higher than usual in the rocks Some seaice was seen on some of the small bergs at the north of the breakout but it was not possible to examine the larger bergs he bergs remained virtually fixed by the seaice until summer but after the breakout of the seaice they rapidly and freely floated away passing to the north of Petersen Island and through Jocelyn Islands Some bergs obviously rolled some tipped partially but many of the larger bergs if not all seemed to just drift out without tipping or rolling There were four large bergs whose nonsubmarine portions measured 1 159m by 238m in area with a maximum height of 50m 2 378m by 401m in area with a maximum height of 58m 3 315m by 211m in area with a maximum height of 25m 4 212m by 262m in area with a maximum height of 57m The accumulation of drift and icelitter at the base of the bergs could lead to an error of up to
29. package with builtin data editing and data rejection facilities It is likely that much of the statistical programs could be aquired from software vendors Alternatively Draper and Smith describe detail methods in both multilinear and nonlinear regression I suggest that future QHM reduction programs particularly when used on Antarctic observations or on observations made during times of high field Appendices C 1 activity use the procedures outlined in Appendix D to compensate field and temperature variations during the observation to reduce scatter in the calculated value of alpha and hence H and to simplify the correlation of variometer output to measured field values Similar procedures can be developed for any other instrument which relies on more than one instantaneous measurement When QHMs are used in the odd pi mode suggest that they be thoroughly tested for angularity of the QHM mirror according to the tests outlined in Appendix E Appendices C 2 APPENDIX D QHMs AND VARIOMETER CONTROL A variety of techniques have been proposed for the use of the QHM either alone or combined with the use of a Declinometer to control the horizontal components of a variometer be 11 or some other device What follows is suggested method of calculating the value of H from a quiet field QHM observation which differs from the method has until now used and method of reducing a
30. quarry blast 12 1320UT Jan 14 1029UT 46226 7nT quarry blast Jan 14 1020UT Jan 16 1900UT d6254 1nT quarry blast Jan 16 1900UT Jan 20 0535UT 46183 6nT 0 8nT Z magnet repositioned Jan 20 0535 1 Jan 31 2400UT 46165 6nT 2 8nT Z magnet agate cleaned Temperature Vertical Thermograph 1984 Feb 01 0000UT Nov 19 2000UT Nov 19 2000UT Jan 31 2400UT new observer optics adjustment 84 17 0 22 102 67 0 42 Temperature Horizontal Thermograph 1984 Feb 01 0000UT Jan 31 2400UT 35 98 0 35 C new observer See Table 7 for residual torsion corrections to the H baselines which have not been applied to the data in this table The baselines for declination measured using declinometer 630332 have been adjusted for an error in observation technique This correction is completely independent of the instrument correction which should be applied additionally in the final derivation of mean hourly values the error in technique involved leaving the base of the declinometer on the circle while siting the mark This required a declination correction of 1 2 WEST these times for baseline changes are approximate The baseline shift could only be definitely ascertained to a period between observations the baseline for this period was derived from the measured baseline shift on the magnetogram as no observations were made during this period the 7 baselines during
31. sin a 2 cos phis cos phi M H cos a sin phi sin phi 2 1 8 _ tan a 2 cos phis cos phi sin phi sin phi 2 e T M H cos a Substituting sin phi cos b m pi for T M H see 3 above tan a sin phi sin phi 2 cos phi cos phi 2 e Ssin phi cos b m pi cos a 2 cos phit cos phi approximating this becomes phi phi cos phi 2 1 cos phi _ 2 e sin phi m pi 2 1 cos phi phit phi cos phi 2 1 cos phi 2 e cos phi 2 1 cos phi 2 e sin phi 2 1 cos phi m pi phi cos phi 2 1 cos phi e cos phi sin phi m pi 1 cos phi 9 Equation 5 gives a as it is normally approximated plus a term ine and a measurable angle phi Hence comparing a as derived by standard formulae for odd and even observations can yield the term in e and therefore e itself The effect on the H calculations can then be determined from 4 Appendices E 2 APPENDIX F EAST BAY ICEFALL JULY 1984 moderate icefall occurred East Bay on 10th July and made a great impression on the seismic charts between 0300 and 0400 UT amount of ice involved in the fall was surveyed using theodolite and sextant largest icebergs were measured and positioned and the extent of the effects of the fall were mapped Figure 9 shows the positions of the icebergs and Figure 10 shows the seismic recording
32. the 15th 30th 45th and 60th minutes DUT1 CCIR code 45 cycles of 900 Hz modulation immediately following the normal second markers pulses of 5 cycles omitted of l1kHz modulation Hour is identified by 0 8s long 1500Hz tone 59th and 29th second pulse each minute identified by 0 8s long 1000Hz tone 0071 CCIR code corrections by double pulse Tables Additional 500 cycles minutes 5 by voice Beginning of information WWVB WWVH YVTO ZU0 second pulses given by reduction of the amplitude of the carrier Coded announcement of the date and time and of the correction to obtain UTI No CCIR code pulses of 6 cycles of 1200Hz modulation 59th and 29th second pulse omitted Hour is identified by 0 8s long 1500Hz tone Beginning of each minute identified by 0 8s long 1200Hz tone DUT1 CCIR code by double pulse Additional information on UTI corrections second pulses of 1kHz modulation with 0 15 duration minute is identified by a 800Hz tone of 0 5s duration Between seconds 52 and 57 of each minute voice announcement of hour minute and second pulses of 5 cycles of 1kHz modulation Second 0 is prolonged DUT1 CCIR code by lengthening For VNG WWV and WWVH DUTI is defined as UT UTC The sign of DUTI is positive if the first emphasised marker of a group is seconds marker 1 sign DUTI is negative if the first emphasised marker of a group is seconds marker 9 The m
33. the period January 12th to 20th 1985 are uncertain due to malfunction in the variometer during this period See comments in section 2 2 La Cour Magnetograph Tables 7 RESIDUAL TORSION CORRECTIONS at Mawson Instrument phi 7 QHM 300 QHM 301 QHM 302 QHM 172 QHM 174 HTM 704 58 25 63 46 56 69 59 47 SEE 40 87 phi diffe 0 11 0 67 0 23 0 17 0 45 0 01 derived residual torsion nT 8 LA COUR MAGNETOGRAPH PARAMETERS 1984 Component ANOT Preliminary Scale Valu 21 2 nT mm 2 43 mm 22 8 nT mm 1 73 C mm 2 48 C mm e rence alpha correction 3 7 0 0 16 1 1 0 significant 8 4 0 2 5 3 0 1 15 5 0 7 significant 1 0 0 0 Preliminary Adopted Adopted Temperature Scale Value Temperature Coefficient Coefficient 40 8 21 21 0 02 nT mm 0 6 nT C 2 423 0 004 mm 1 0 nT C 22 65 0 08 nT mm 1 1 nT C I 1 738 C mm 2 36 C mm 9 PRELIMINARY INSTRUMENT CORRECTIONS 1984 Instrument QHM 300 QHM 301 QHM 302 Askania Dec 630332 BMZ 62 Correction at Correction 18433 5 nl 000271H 3 000163 enl 000434 0 0 2 Tables 10 PRELIMINARY MEAN MONTHLY AND K INDEX VALUES 1984 5 H D W 7 K INDEX nT um nT nT av med max 1984 Cechet January 18437 63 29 7 46426 49953 3 8 1984 Crosthwaite February 18445 63 29 2 46438 49967 3 9 3 8 March 18448 63 32
34. true X PEM baseline apparent baseline e Y true Y PEM baseline apparent Y PEM baseline e X where the sign of may be confusing Appendices APPENDIX C FUTURE PROCESSING OF PCH DATA The computer programs available for processing data on the CSIRONET are not well documented not particularly reliable and not completely relevant to the data plotting facilities both on CSIRONET and the computers do not provide fast enough turnaround to enable processing of data to proceed with reasonable speed and minimal loss of enthusiasm Consequently there is a need for new computer processing software for the Antarctic data Of course there is nothing special about Antarctic data so the processing would overlap to a large extent with Canberra Gnangara etc data processing Several ad hoc programs written by the author to process 1984 PEM data would be useful if rewritten a more leisurely better documented more generalised fashion Programs that are transportable between the system CSIRONET and small personal computers hopefully to installed at the remote observatories and for possible use in field surveys are highly desirable Also interactive plotting facilities that can be woven into statistical analysis programs on personal computers and possibly on mainframes as well would greatly increase the speed of parameter determinations and increase the depth to which the data
35. 1 QHM302 DEC332 The BMZ was removed from the hut to its shelter in the cold after completion of 7 observations so that the other measurements were not disturbed With the availability of the PEM analogue display it was possible to select only very quiet periods during which to do absolutes Emphasis was given to selecting quiet periods rather than rigidly doing absolutes twice per week Hence on occasions more than a week passed between sets of absolutes Additional observations were performed when baselines changed Before the 18th September all QHM observations were corrected for declination variations measured from the La Cour magnetograms Subsequently the variations were calculated from PEM data In February 1984 and February 1985 instrument intercomparisons through baselines were performed with the travelling standards These results are tabulated in Tables 4 and 5 and take into account residual torsion of all the QHMs Baseline derivations in Table 6 use the standard QHM programs and do not Mawson Magnetic Observatory include this correction Table 7 lists the torsion corrections to all observatory QHMs and travelling standards The constants for the scale value coils for D and Z variometers are listed in Table 3 During every scale value observation the calibration current was monitored using a Fluke digital multimeter approximate calibration currents used were 60mA for 40mA for D and 70mA for
36. 15 mm min Calibrator Motor constant N A 1 50 0 21 Coil Resistance ohm 247 323 System Polarity Up up Up up Bracketted values are those taken from previous reports Tables 17 SEISMOGRAPH PARAMETERS post February 1985 Component SP Z SP NS SP EW LP Z Seismometer Type _ Benioff Benioff Benioff Press Ewing Free Periods 1 0 1 0 1 0 12 0 Mass 107 5 107 5 107 5 6 9 Coil Resistance 1000 ohms 1000 ohms 1000 ohms 500 ohms Power supply PP2 PP2 PP hoc Preamplifier Type 5 5 5 5 Gain setting 96dB 7 2dB Attenuator setting gain attenuation recorded on seismogram Bandpass filter 1 10 Hz 01 20 Hz Recorder Amplifier Type Geotech Geotech Geotech Geotech Mode AR320 AR320 AR320 AR320 Attenuator setting Recorded on 1 lt Recorder Type Geotech Geotech Geotech Geotech Model RV 301 RV 301 RV 301 RV 301 Chart Rate 60 mm min 30 mm min 60 mm min 30 mm min Calibrator Motor constant N A 1 50 not measured not measured 0 21 Coil Resistance ohm 247 249 258 3 3 System Polarity Up up North up East up Up up Bracketted values are taken from previous reports The coil values are nominal values only The actual less than the nominal values Tables values are slightly 18 SPZ SEISMOGRAPH CALIBRATION October 1984 Period secs Magnification Magnification measured corrected 0 2 23 4 1000 20 1 x 1000 0 25
37. 2 38 5 2 8 493 15 3 4 2 Values are given with no instrument corrections applied Tables 15 HORIZONTAL SEISMOGRAPH PARAMETERS 1983 May 1984 Component SP NS SP EW Seismometer Type Benioff Benioff Free Periods 1 0 1 0 55 107 5 107 5 Galvanometer Type Geotech Lehner Griffith Free Period s 0 2 0 2 Recorder Type Benioff Benioff Model Photographic Photographic Chart Rate 60 mm min 60 mm min Calibrator Motor constant N A 1 27 1 25 Coil Resistance ohm 249 258 System Damping 8 1 8 1 Magnification at 1 sec 25 5K 21 8K Peak Magnification Period 157K 0 2 49K 0 5 Polarity South up Fast up The contents of this table are taken directly from Silberstein 1984 No later calibrations or system changes have been made magnification settings on the system until May 1984 are identical to that reported by Cechet 1984 Tables 16 VERTICAL SEISMOGRAPH PARAMETERS pre February 1985 Component SP Z LP Z Seismometer Benioff Press Ewing Free Periods 1 0 12 0 Mass kg 107 5 6 9 Power supply ad hoc Preamplifier Type 5 5 Gain setting 96dB 7 08 Attenuator gain attenuation recorded setting on seismogram Bandpass filter 1 10 Hz 01 20 Hz Recorder Amplifier Type Geotech Geotech Model AR320 AR320 Attenuator setting Recorded on seismogram Recorder Type Geotech Geotech Model RV 301 RV 301 Chart Rate 60 mm min
38. 9 1984 7 0 2 7 4 2 31 8 20 8 98 4 90 0 1984 results have correction of 6nT applied to the annual average as the preliminary means used a correction of OnT for BMZ62 This correction is applied nowhere else in this record Tables 12 PEM AND La Cour DATA COMPARISON Date 04 05 06 07 Hour K H dif D dif K H dif D dif K H dif D dif K H dif D dif 8 nT x 01 6 48 8 1 4 1 0 7 3 6 0 9 02 3 0 7 9 0 6 5 0 1 03 13 0 2 1 0 3 4 0 2 04 14 1 0 1 4 3 1 0 13 3 0 4 05 5 0 3 1 0 6 5 0 2 06 0 0 6 4 0 8 0 2 07 14 1 0 4 3 6 0 4 2 3 0 9 08 3 1 8 1 0 1 2 0 1 09 5 2 0 6 0 8 1 0 0 10 14 1 1 1 1 0 9 1 0 0 5 11 14 8 2 1 3 4 0 6 12 3 0 8 5 1 1 6 0 2 13 13 pe of 0 8 2 3 0 9 1 1 0 3 14 12 2 0 17 1 4 6 1 1 7 0 0 15 6 0 9 12 1 2 1 0 4 0 0 5 16 4 2 0 6 2 11 1 8 3 7 1 5 1 2 0 1 17 8 1 0 9 1 0 1 1 6 1 0 2 18 7 0 8 9 2 1 5 8 0 1 19 133 5 0 4 4 9 0 9 4 14 1 2 1 7 0 5 20 4 0 4 19 155927 7 0 8 1 0 2 21 5 0 3 3 0 8 Iil 1 0 22 7 26 0 0 4 7 1 0 5 10 0 4 23 19 0 7 4 0 9 13 1 6 24 8 1 15 3 6 6 0 6 4 0 5 4 0 5 1 0 This table lists the difference between La Cour and and D data from the 4th to the 7th August 1984 corresponding indices are also provided The adop
39. C F R 1 kl t for a constant T D MO assuming that D and MO are constant which is valid over a short time period and that is small as it is Let Bt be the baseline at temperature t Bts be the baseline at standard temperature ts corresponding to reference feedback field which is the measure of the field variation of Fr Then Bt Fr R 1 and Bts Fr 1 kl ts hence Bt Bts R kl t ts i e R kKkl As is small often zero compared to Bt and is small is very nearly the value of the baseline Hence the temperature coefficient is the product of the baseline and the QHM constant The geometry of a PEM system is very simple as the feedback system keeps the magnet steady The analysis is therefore simple compared to a La Cour system Assuming a PEM has a true baseline Bt for the component of the field C it is measuring then Bt H cos b e s c horizontal field where H b angle between the horizontal field and the nominal PEM Appendices alignment e error in PEM alignment scale value of the PEM C output of the PEM measuring the field variation hence Bt H cos b cos e sin b sin e s c H cos b cos e s c H sin b sin e Bt cos e D sin e where Bt calculated baseline assuming the nominal orientation complementary component of the one measured by the PEM For small values of e this translates to
40. Group of Scientific Experts Technical Test GSETT from October 15th 1984 until December 15th 1984 special effort was taken to report all events including very weak events that would normally not have been considered he information scaled from the seismograms principally the SPZ and to a very limited extent the LPZ seismograms was telexed to all International Data Centres In all 550 events were reported during the test and they described by 2924 parameters Of these reported events 145 were actually used in epicentre determination this was 13 per cent of all of the global events recorded by all stations participating in the test During the entire year P and occasionally other phase arrival times were reported to Canberra weekly and the data was relayed to US Geological Survey National Earthquake Information Service Denver Colorado In all 1600 events were reported from February 1984 to January 1985 Of these 1183 occurred between August and December During the months when there was no sea ice February and March 1984 and January 1985 fewer than 50 events per month were reported and on about half of the days no events at all were reported Reported SPZ amplitudes were incorrect following the October calibrations due to an incorrect determination of G See Table 18 LPZ amplitudes have been Seismological Observatory reported incorrectly since the installation of the seismometer as the seismometer mass has always b
41. a decaying term in the baselines which one would intuitively feel to be exponential Hence the aim of the baseline reductions was to find an expression which gave the asymptotic baseline and to choose the constants in the expression to give the minimum scatter in the reductions Mawson Magnetic Observatory calculated preliminary differences between individual observations within the same set throughout the year after exclusion of some wild values derived from the PEM data displayed a standard deviation of 1 to 2 nT See Table 5 The EDAS exhibitted a drift corresponding to about 0 5nT in its analogue to digital conversion The tolerences in the derived constants could not expected to be any smaller than those that would lead to a scatter in the final reductions of at least a similar amount The expressions that were chosen to reflect the asymptotic baselines were X sx x xs qx 1 15 ex Y Ys Rx exp d Dx Y sy y ys qy t ts ey X Xs Ry exp d Dy where X Y are the measured values of the NS and EW components of the field 5 are the scale values of the X and Y PEMs are the temperature coefficients of the X and Y PEMs ex ey are the errors in aligiment of the X and Y PEMs in radians RX Ry are the terms arising from the relaxation of the QHM fibres Dx Dy are the time constants for relaxation of the X and Y QHM fibres are the EDAS values corresponding to the horiz
42. agnitude of DUTI is given by the number of consecutive emphasised seconds markers each representing 0 1 second Tables WELCH ISLAND DRUMS TALL PEG SN 239 25 5 5000m Js NEW VARIOMETER HUT 67 36 2 5 hu NU 629 52 7 E Acie NaS S EA UN 47 SHORT PEG Pee NONG N M UN ABSOLUTE HUT 679 36 2 S 629 52 8 E 037 70m 2419 d BMR 1985 2 Fig Reference Marks and Azimuths 24 09 237 Record 1986 12 SEISMOMETER PLATFORM EQUIPMENT RACK S 6 SOUTH REFERENCE E RAILS SET AT 240 TRU MING COSMIC RAY TELESCOP N RVEYED 550 SU CABLE 7 TERMINATION 7 2 7 2 Fig 2 Seismic Vault layout Record 1986 12 24 09 241 5 5 i2 V TAM5 TAM 5 LO LO OUTPUT INPUT SUPPLY INPUT OUTPUT IOSL 3P 145 7S 14 7P 145 78 WH B B GN 2 WU WOO d BANANA PLUG FOR T amp DAMPING RESISTOR M lt CIRCUIT BOARD 0 FOR ADDITIONAL lt 5 RPCIRCUIT BOARD FOR INPUT POWER CIRCUITRY GN XXX REAR TAMSH I OUTPUT NOT CONNECTED PLUGGERY Fig 3 SPH electronics rack wiring diagram Record 1986 12 24 09 243 1000 loo ix gt 2 o e C a lO 0 1 1 0 Period s Fig 4 SPZ Calibration curve October 1984 Record 1986 12 24 09 238 100 10 2
43. ariometers on the 18th September 1984 The orientation coils were assumed to be aligned at 296 True The current for the test was derived from Minilab constant voltage source fed through a variable resistor The currents used were 350mA The results are consistent with previous years See Table 2 Z variometer was tested on the 12th and 24th of November 1984 The deflector magnet was measured by the following method to be 484 2 nT m3 It was previously measured as 491 4 nT m3 Wolter 1981 1 the deflector magnet was positioned exactly magnetic east of Pier in a magnetic East West orientation at the same level as a QHM magnet resting on the pier and levelled 2 the field was measured without the presence of the deflector magnet then with the magnet East West then West East and then with the magnet absent again 3 the PEM data was used to correct for H and D variations Before the 7 tests the holder for the deflector magnet was levelled and oriented correctly with respect to the 7 variometer magnet Both tests were consistent but differed markedly from 1982 and 1983 results The coil constants are given in Table 3 2 2 3 Baseline Control Absolute observations and scale value observations were performed on average seven times per month to determine D and 7 baselines on the La Cour magnetograph and X and Y baselines on the PEM observing schedule was 1 BMZ62 BMZ62 2 DEC332 Q0HM300 QHM30
44. arisons were attempted at Davis in January 1984 with the assistance of Warwick Williams during a very brief stop BMZ QHM and D comparisons were performed at Casey in March 1985 the return voyage A check of the automatic magnetic observatory at Macquarie Island was also made on the return voyage D and comparisons were performed at Mawson both at the beginning and end of the author s term Introduction 1 1 CHAPTER 2 MAWSON MAGNETIC OBSERVATORY The H D and 7 components of the geomagnetic field were continuously recorded using a La Cour magnetograph accompanied by frequent baseline and scale value observations two component X and Y horizontal PEM magnetometer was operated and recorded both digitally and on analogue charts from May 1984 purpose of operating this system was to gain experience operating PEM s which are relatively new and unique to BMR and to determine the operating parameters of the magnetograph which would soon replace the La Cour PEM was 8 very useful tool and was used to calculate delta D corrections to QHM observations once its scale values were determined and to calculate delta D and delta H corrections during instrument comparisons and measurements of the strengths of the magnets used for La Cour orientation tests A reference azimuth line was laid in the floor of the new variometer building and a new mark for declination observations was installed to replace an ol
45. as completed in Autumn 1985 after the departure of the author It will be fitted out during 1985 with the four component PEM PPM system The Variometer Power Supply Building resides in the midst of the quarry It is very vulnerable to damage from vehicles and flying boulders and indeed was damaged on several occassions by quarrying activities hut originally housed the 12V power supply for the La Cour lamps but this was moved in April 1984 to the Science Building Its only function now is to house a switchboard for the Station power supply to the variometer building With the transfer to the New Variometer Building it will no longer be required by BMR The Old Seismic Vault once housed the seismometers Since May 1984 it has not been used for any specific reason The only reason for retaining it is the presence of a GRAVITY STATION on the instrument pier Advice from Dr P Wellman of the was that the station was not vital alternative gravity stations exist at Mawson It is currently used as a store room and the Antarctic Division If it is to remain service it will require painting in the near future The Cosray Building houses all of the seismometers a preamplifier calibration rack deep in its mine shaft and a 12V power supply in the office 1 suggest that a ceiling be added to the BMR side of the shaft to stop dust from being washed down onto the instruments during the summer melt and that shelving b
46. assume that the Silberstein 1984 24db attenuation 0 01 20Hz passband 30db attenuation 12 0 secs 5110 ohms currents used 600 microamps approx p p value 31mg 62mg 0 2 to 0 5 mA masses used currents used The calculations is different from the assumed mass of 11 2 kg used in previous reports see Cechet 1984 for Magnification Conversion Tables for 5 and AR320 Tables 21 TIME SERVICES FREQUENCIES PROPAGATION DELAYS Station Location VNG WWV WWVB WWVH YVTO ZUO VNG WWV Lyndhurst Australia 38 3 145 16 Fort Collins USA 40 41 105 2 Fort Collins USA 40 40 105 32 Kauai USA 21 59 159 46 Caracas Venezuaela 10 30 66 56 Olifantsfontein South Africa 25 58 28 14 second markers second markers 55 to 58 During the Frequency Schedule kHz 1500 7500 12000 2500 5000 10000 15000 20000 25000 60 2500 5000 10000 15000 20000 6100 2500 5000 10000 9h45m 21h30m 22h45m 22h30m 21h15m 9h30m continuous continuous continuous 12h00m 20h00m Oh30m 1h30m 18h00m 01 00 continuous continuous 50 cycles of Seconds marker for minute markers cycles for seconds markers 50 58 Delay Bearing ms 22 101 60 201 50 128 45 236 20 316 kHz modulation 5 cycles 59 is omitted Sth 10th 15th Identification announcement during
47. bruary 1984 to January 1985 using reductions from La Cour variometer magnetograms QHM 300 301 1 7 0 6 QHM 300 QHM 302 5 4 nT 0 5 nT The above calculations not subject to torsion correction see Table 7 Standard Deviations are those of the various baselines calculated between baseline discontinuities Statistically grouping the observations this way would be expected to reduce the standard deviation by a factor of four or five Through routine baseline determinations from June 1984 January 1985 using reductions from PEM EDAS digital recordings QHM 300 QHM 301 0 7 nT 1 6 QHM 300 QHM 302 4 9 nT 1 8 The above calculations are subject to torsion correction see Table 7 Standard Deviations are those of the individual observations the results compare more favourably than would appear with the La Cour results As a quality check on observer performance variometer sensitivity and absolute instrument reliability one may note the following observation scatters Tables Instrument Difference between observations in the SAME set Average Maximum HTM 570704 0 7 nT 1 3 nT 172 1 0 nT 1 7 nT 300 0 6 nT 1 1 nT DEC 640505 20 4 2027 DEC 630332 0 2 0 5 This is a considerable improvement on February 1984 results due to an observer with one year s more experience and a much better variometer to control the comparisons namely
48. can be studied The following programs on the system were found necessary 1 a observation reduction program 2 an Askania declinometer reduction program 3 a program to process sets of Askania declinometer and QHM observations using the PEM data as control to find PEM baselines 4 a linear regression program to calculate temperature coefficients scale values exorientation angles etc 5 data editting program to reject data that lies too far off given straight line as a preprocessor for the above regression program 6 a semi logarithmic regression program to calculate the exponential decay of PEM fibre torque 7 a quick and nasty plot program using Dr Hopgoods basic subroutine to get a variety of data plots from input text data with a minimum of effort Many of these programs could be combined into larger more general programs For example the Declinometer reduction programs could be combined into a program to process absolute instrument observation recorded observation schedule form supplemented by any relevant data such as variometer data Another program could process sets of absolute observations supplemented variometer data to produce lists of all seven basic components 7 D I X and Y standard time with the relevant variometer outputs regression plotting programs could be combined to a multilinear regression analysis and plotting
49. correction of many tens of nanoteslas in both locations and a final error after extrapolating the Canberra comparisons to the PNG field of many tens of nanoteslas It is advisable in future to include this term in all computer QHM reduction programs and to determine a standard correction for each QHM in the field in which it is used for hand calculations table of such corrections for instruments used at Mawson is included in this report 5 Table 7 It should be noted that the change method of calculation may cause apparent discontinuities in the long term comparison graphs Appendices D 1 Quiet ing a noisy field The availability of digital data and computer processing of observations makes it more desirable to reduce a QIM observation to a single moment in time moment can be redefined these days as a digital aquisition period The advantages are 1 all circle readings then refer to the digital output of the variometer at a Single moment Otherwise averages of several moments must taken and the moments chosen for looking at the H observation are different from the moments chosen for looking at the D side of a QHM observation which leads to a few complications in keeping track of the data 2 since all circle readings then become relative to the same field both zero readings both n pi readings and both n pi readings should be identical and the n pi and n pi deviations from the zero reading should dif
50. d mark which has been obscured by the new variometer building In conjunction with this the azimuths of old marks were checked The geographic coordinates of the magnetic buildings were surveyed and determined more accurately than previously so that greater accuracy in sunshot calculations could be achieved These are listed in Table 1 2 1 Absolute Instruments The instruments used were QHMs 300 301 302 using thermometers 2143 1416 and 1401 respectively Askania Declinometer 630332 Askania circle 611665 and BMZ 62 using thermometers 2501 and 2161 according to the prevailing temperature The proton precession magnetometer MNS2 1 had not worked since mid 1983 and was never used during 1984 All attempts to fix it early in 1984 failed After a last attempt to fix it just before the 1985 changeover the instrument finally began to work with some small degree of reliability he BMZ required frequent cleaning and the telescope mounting was loose leading to a very large variation in the neutral division Otherwise it performed adequately The QHMs gave few problems The clamping mechanism on QHM 301 is sticky and introduces nuisance vibrations at the beginning of an observation which take several minutes to damp out The thermometer on QHM 301 15 obviously inconsistent with other thermometers Cechet 1984 and an instrument correction discontinuity will be expected when it is eventually replaced The declinometer worked satisfactorily th
51. der drum motor timemark closures and 12V for the recorder lamps CAUTION This cable has an unusable 7th core which is shorted to the 240V pair Control Equipment 5 4 5 the multichannel shielded cable from the Science Building to the Old Variometer Building carrying PEM information and control signals This cable was cut numerous times during the year and has some discontinuous pairs and some pairs which are shorted to each other It is not in good condition 6 the cable from the Science Building to the PPM box that used to carry PPM data a heater relay switch drive and maybe other things This cable had at least three cuts only two of which could be found at the author s departure It was left in an unusable condition 7 the cable between the Absolute Hut and the Old Variometer Building which carries event mark signals to the La Cour recorder All of those cables between the Science Building and the Old Variometer Building run through the quarry site via several underground road crossings They are all in grave danger of being damaged and indeed frequently were during 1984 The cable route is no longer viable No new cables should follow this route and it is doubtful that any of the cables could be recovered in usable lengths These cables will not be required when the Old Variometer Building is shutdown i The 10 pair cables for the magnetic and seismic systems are 10 twisted pairs of insulated solid conductors It was f
52. e The British have full magnetic observatory on a moving rotating ice shelf at Halley in the Weddell Sea Other Antarctic Observatories CHAPTER 4 SEISMOLOGICAL OBSERVATORY Mawson seismic observatory consists of a four component seismograph system see Table 1 for details of seismograph locations Vertical seismometers a Press Ewing long period seismometer a Benioff short period seismometer Horizontal seismometers two Benioff short period seismometers The vertical seismometers were in operation throughout 1984 and were located in the Cosray vault 13m underground and recorded on Geotech Helicorder hot pen recorders The horizontal seismometers were in operation until 7th May in the Old Seismic Vault and were recorded on a Benioff three drum photographic recorder the 23rd June with the help of several other expeditioners they were moved to the BMR seismometer room in the Cosray vault During changeover in February 1985 the SPZ seismometer was moved to make room on the seismometer platform for the two horizontal seismometers and the horizontal seismometers were orientated and connected to a separate pre amplifier rack Helicorders were converted to dual pen operation and all four seismometers were subsequently recorded on the visual system with the LPZ and SPN seismometers on one recorder set at 30 mm min and the SPZ and SPE seismometers on the other set at 60 mm min See Tables 15 16 and 17 for the seism
53. e installed into the cavities in the rock walls to improve working conditions in the vault At frequent intervals during the melt the sump in the shaft has to be emptied by hauling buckets of water up on a pulley system This has been so since the sump pump ceased operation It would be worthwhile persuading the Antarctic Division to install a new pump In the Science Building affectionately known as Wombat has possession of a workroom office and a darkroom very time consuming part of geophysicists life at Mawson is spent working out what is in Wombat where it is stored how it works and what to do with it On the author s arrival the workroom was unwalkable and unusable As appears to be the case with my Buildings and Building Maintenance predecessor a great deal of time was spent discarding or preparing for as much old junk as possible to make room for as much new junk as possible as it appears that out of the way places such as Antarctic Observatories are the last resting ground for such things Of course the geophysics rooms were totally reorganised to suit the occupant and no doubt they have already been reorganised by the new occupant There is more than enough furniture in the office and an excess of archaic equipment It could be hoped that only useful and reliable equipment will be allowed to clutter the halls of Mawson science in the future the way Wombat is at the end all of those cables ori
54. e noise was observed to come from two distinct sources One was the Stabilac voltage stabiliser see Chapter 5 CONTROL EQUIPMENT and the other was radio transmissions in particular ARQ radio transmissions to Casey Various attempts to fix the problem by earthing various parts the system failed and the dirty contacts rectification phenomenom described in previous reports was investigated without success effects of the problem were minimised by maintaining high attenuation the recorder amplifiers and a high gain in the 5 preamplifiers This caused some problems during isolated noisy days principally during blizzards as the attenuation at the recorders could not be increased enough but as the likelihood of recording an event against a high noise level was minute further action was taken The gearing and transmission in the LPZ helicorder gave several problems and caused the loss of data on several occasions until al the necessary adjustments and repairs were located and performed A temporary rack for the horizontal seismometer amplifiers was assembled see Figure 3 and with the help of Peta Kelsey the helicorders were converted to dual pen operation the SPZ seismometer was moved and the SPH seismometers were prepared for installation by connecting their eight nominally 125 ohm coils in series and orienting them north south and east west the seismometer platform The horizontal system was merged
55. e to the brevity of the stopover The comparisons were performed by simultaneous observation and the results are listed in Table 13 They were not very successful Only two observations of each BMZ was made at each of the two stations eight observations in all The two derived station differences differed by 60nT 3 2 Casey QHM and D and BMZ comparisons were carried out on the return voyage from Mawson in March 1985 Consecutive observations were made according to the following schedule 1 BMZ and QHM comparisons instruments QHM172 PPM1023 BMZ64 BMZ236 order H172 F1023 7236 764 764 7236 F1023 1172 H172 H493 H493 H172 H172 three sets of observations were performed In addition one set of observations order 172 1023 764 764 7236 7236 2704 1023 172 was performed 2 Declination comparisons instruments Askania declinometer 640505 circle 508813 QHM493 order D505 H493 H493 D505 three sets of observations were performed The following problems were encountered 1 The field was not unexpectedly active and the absence of both variometer control and a second observer to perform simultaneous observations there was a large scatter in the derived field values 2 observation procedure recommended was very slow particularly where BMZs were used The BMZs could either be moved from the warm hut to the cold outside storage pier and back again resulting in large temperature stabilisation problems and conde
56. een assumed to be 11 2 kg Manufacturer s specifications indicate that the actual seismometer mass is 6 9 kg The system magnification should have been reduced by 6 9 11 2 in past calibrations It is still quite likely that the assumed distance to the centre of gravity of the boom mass system is not 308mm as has been assumed in 1984 and previous calibrations and so the determined magnifications are probably still incorrect One significant ice breakout was recorded only a few kilometers from the station Details of the breakout are described in Appendix Seismological Observatory 4 4 CHAPTER 5 CONTROL EQUIPMENT On arrival at the observatory the author was faced with a terminal board that collected and redistributed all the 240V backup 240V 115V 24V 12V supplies and in addition the data signals and timing signals high voltage and timing signals passed through the PPT 1 board power and timing control and a power monitor board Most of the high voltage was put through exposed terminals and none of the wiring was relocatable with ease as it was all terminated in screw terminal boards This wiring was not only untidy and incomprehensible being undocumented but also extremely dangerous to anyone who needed access to the rack This board was gradually dismantled 240V devices were fitted with standard 240V plugs and the power was supplied through standard wall sockets The 110V system was similarly treated alt
57. enna was used to receive time signals from various time services The quality of reception was extremely poor and at times no time signal was received for 15 or 20 days This was mainly due to the radio receiver although one Polar Cap Absorption event obliterated all HF radio reception for week borrowed HF communications receiver available during the worst reception period midwinter courtesy of IPS performed manyfold better than the BMR counterpart even though it did not have any notch filters to select the audio time signal Generally VNG Lyndhurst Victoria was used to provide accurate time corrections for the GED crystal oven clock Occasionally WWV was used although it was sometimes difficult to be certain whether the time signal originated from WWVH Hawaii or WWV Colorado or indeed 700 Olifantsfontein South Africa which transmits on the same frequencies See Table 21 for stations frequencies and propagation delays to Mawson Advice from physicists at Macquarie Island suggests that a more reliable method of receiving the time signals may be via an Omega very low frequency receiver It may be well worthwhile looking into this possibility in the future if the performance of the HF receivers and antennae continue to be unreliable 5 2 2 GED digital crystal oven clock The GED clock was used to provide timemarks to the seismic system and to the La Cour recording system inverter card one of the clocks
58. er cent over the Doric readout Hence the temperature coefficients derived from the observation data are actually For 2 99 1 For Y PEM 4 8 10 nT C 2 3 4 Orientation calculations If the above accepted constants reasonable then the X has an orientation error of 0 23 and the Y PEM has an orientation error of 2 9 2 3 5 PEM baseline drifts The PEMs were installed in July 1983 Cechet 1984 From the determined constants the X PEM would enjoy baseline drift of InT month due to fibre relaxation about 18 months after installation and 1nT year after further two years The Y PEM would take three years to stabilise to InT month and six years to stabilise to InT year 2 3 6 Improvements to the digital recording system The EDAS recording system performs well on the analogue digital conversion side having a short term drift of about 0 5 nT but it records and displays the data in an inflexible manner and provides no means of playing back the data for Mawson Magnetic Observatory 2 9 processing or verification It is restrictive in that the display of data cannot occur at a different rate to the recording rate and the display format causes almost unacceptable levels of paper consumption Also there have been great many problems reading the EDAS cassettes it is time consuming error prone process It is desirable to be able to perform absolutes over the entire range of recorded data
59. ers 5 1 1 Stabilac voltage stabiliser The Stabilac was of questionable use It was not capable of providing noise free power at 240V and was turned down to under 210V to prevent induced noise in the seismic recorders At one stage the voltage output surged to 300V and melted the seismic recorder pens Another similar surge nicely toasted a couple of seismic charts i e if you like your charts crisp It was unsatisfactory when used as backup to inverter supply as there was too great a voltage difference between the output of the two devices These problems occurred both before and Control Equipment 5 1 after all of the valves in the unit were replaced installation of a line filter the output of the unit did not solve the noise problem It was retained in use as the station power voltage variations caused fadeouts on the seismic charts 5 1 2 Advance Electronic Inverter he inverter functioned very well for about a month providing reliable and high quality power Initial problems were caused by its very high synchronising load which could not be supplied by the clock s 50Hz output Its characteristics seemed to change and fuses began blowing more and more frequently until it completely failed This was very disappointing as 1 provided a means of making the entire system totally unaffected by brief power failures 5 2 Timing Control 5 2 1 Time Signals Labtronics radio receiver connected to a borrowed long wire ant
60. f 6 4nT to X and 1 7nT to Y In order to achieve more reliable estimates of the constants it would be necessary to both reduce the scatter in the observations and to extend the range of field values over which the observations are made This means making observations during non quiet periods and reducing the sampling interval of the digital display See Appendix for details of the computer programs used to perform the above analysis 2 3 3 Temperature coefficients he temperature response of the system depends on the magnet coefficient the response of the PEM electronics and the response of the analogue to digital conversion electronics These temperatures necessarily dependant The primary component of the coefficient will be from the QHM magnet See Appendix B for the justification of the following statement The temperature coefficient is the product of the QHM temperature coefficent and the PEM baseline value For X PEM using QHM 292 d 3 02 nly For Y PEM using QHM 291 7 97 nT C Doric temperature sensor used at Mawson in 1984 was never calibrated against a thermometer but in adjusting the electronics it was found that the temperature corresponding to expected thermistor characteristics was beyond the range of adjustment of the Doric The unit was slightly nonlinear but over the range of measured temperature the actual temperature should probably be increased 5 p
61. fer by a predictable amount This makes quality checking of the combination of an observation and the variometer very simple and highlights errors each part of the observation The analysis that follows ignores the effect of induction and commences by differentiating the equation of equilibrium of a QHM magnet M H sin p 1 0 E where moment of the QHM magnet 0 1 1 4 ignoring induction 1 QHM temperature coefficient horizontal field strength T QHM fibre torsion constant Q torsion in the QHM fibre p angle between the magnet and the horizontal field t QHM temperature dH H kl dt 1 k1 t cot p dp 40 0 i e dp tan p dH H kl dt 1 kl t 40 01 2 First consider the zero reading Then 8 i e alpha Q B the residual torsion in the fibre dp dQ dB da from 1 M H sin a l 3 from 2 dp tan a dH H kl dt 1 kl t dp B i e dp tan a dH H kl dt 1 kl1 t 1 tan a B 4 Next consider the n pi reading Then 1 a n pi p Q from 1 n pi M H sin phi a T Appendices D 2 from 2 dp tan phi a dH H kl dt 1 k1 t 08 1 8 6 Next consider the n pi reading Then from 1 n pi M H sin phi a T 2 from 2 dp tan phi a dH H kl dt 1 kl1 t dB n pi B 8 Substituting for dB from 4 into 6 dp
62. for the 78 hours considered were 0 5 1 3 for D and 1 0 9 5 nT for After exclusion of few wild values the differences were 0 6 0 7 for D and 0 4 nT 7 9 nT for comparison results are well within the expected tolerences although the sample size is not large enough to be thoroughly convincing Mawson Magnetic Observatory 2 11 2 5 Temperature Control The variometer building is heated by four bar heaters controlled by a 1 thermistor control unit temperature sensor 15 located on the ceiling above the La Cour magnetograph It failed only once during the year when the temperature in the hut began to be controlled at about 8 C The cause was never discovered as the unit recovered of its own accord Only three heaters were connected to the 1 and the fourth was only used during the failure another heater As far as possible the same set of heaters was used to try and keep the huts isotherms fixed and therefore make temperature corrections more meaningful Note that the temperature of all La Cour variometers is measured from the one thermograph and the temperature of both the X and Y PEMs is measured by the same thermocouple The PZC 1 unit restricted the daily temperature variation in the hut to 1 or During summer the temperature of the hut rose to well above 5 C but nothing could be done about this 11 of the heater elements required replac
63. ginating from the out buildings and houses the digital and analogue recorders the seismic recorders and most of the control equipment low voltage and backup power supplies Buildings and Building Maintenance CHAPTER 7 OTHER DUTIES The author was the Sea Ice Observer for 1984 This involved taking measurements of the depth of the sea ice either weekly monthly at various sample points in the Mawson area and noting the formation decay pattern of the ice It also involved at times reconnaisance of the ice to judge its safety regarding travel recreation The author was also the iceberg watcher counter and measurer on the voyage from Australia to Antarctica The usual station duties were performed This included one night per month nightwatch 14 days full time kitchen duties Saturday afternoon council duties garbage disposal etc Some assistance was given to the lonospheric Prediction Service performing daily routines during the absence of their observer Other Duties 7 1 ACKNOWLEDGEMENTS The author wishes to express his thanks to the Mawson 1984 and 1985 wintering and summering parties for their assistance and co operation In particular special thanks are due to Grant Lamont for his frequent and helpful advice on electronic matters and assistance in performing the daily routine during the author s absence to Robin Thomas for his assistance in performing the daily routi
64. graphic system was disconnected in May 1984 seismometers were relocated and connected to the visual recording system February 1985 Preliminary magnetic data were forwarded monthly to Australia Preliminary seismic data were forwarded weekly to Australia and all Antarctic geophysical stations addition special seismic data were forwarded daily to Australia and all other International Data Centres during the Group Scientific Experts Technical Test nuclear monitoring from September to December CHAPTER 1 INTRODUCTION Mawson Geophysical Observatory is operated by the Bureau of Mineral Resources Division of Geophysics part of the Australian National Antarctic Research Expeditions ANARE at Mawson Australian Antarctic Territory Logistic support is provided by the Antarctic Division of the Department of Science and Technology Station details are listed in Table 1 The observatory commenced operation in 1955 with the installation of a three component La Cour magnetograph from Heard Island Oldham 1957 Since then numerous instrument changes have taken place see Appendix A author arrived at Mawson 15 Februry 1984 on the Nella Dan to relieve 800 Cechet who departed the 3rd February The replacement geophysicist Peta Kelsey arrived the Ice Bird on the 6th Febuary 1985 and after extended changeover the author departed on the 5th March on the Ice Bird BMZ comp
65. he output data reduce the amount of work to be done on RTA and free the geophysicist to perform research or assist other scientific duties It is important to chose a multi tasking computer for the acquisition system so that modern versatile and useful system capable of real time display and instant data recall can be developed this would be far in advance of anything available at Mawson to date The computer would either need its own analogue digital conversion ability or an external device to perform the conversions In the short term the EDAS itself could function as such a device but in the long term cheap micro controlled unit such as the one developed in BMR for digital seismic acquisition or the relevant parts of the array magnetometer developed at Flinders University by Francois Chamalaun could be installed The latter option could retain data in a buffer and be backed up with a low voltage power supply to avoid the more expensive power backup requirements of the computer If it was designed such that information such as mean hourly values could be extracted using a printer terminal it could also provide backup in the case of main computer failure or a cut cable and run off the same emergency power supply as the PEM in the case of a mains power failure Transmitting the information from the variometer hut the Science Building in digital form via a modem interface along a single pair cable would reduce the noise introd
66. heating system could be installed The heaters from the old variometer building will soon be available 2 6 Surveyed Reference Marks See Figure 1 for details of reference marks See Major 1971 for other versions of azimuths and reference marks in the Old Variometer Building Mawson Magnetic Observatory 2 2 6 1 Variometer Building primary mark and a reference mark were embedded in the floor of the building to provide reference azimuth for installation of the Photo electric Magnetograph marks consist of hexagonal brass plugs 25mm diameter 25mm with turned raised centre marks surrounded by blue tinted epoxy resin coated with a clear layer of epoxy Nl is located in the northeast corner of the building i e the instrument room is located the southeast corner i e the electronics room RI is visible from N1 through the doorways of the two rooms The azimuth of from Nl was measured by sunshots using the Department of Housing and Construction s Sokkisha Theodolite before the erection of the walls to be 131 49 10 10 2 6 2 Declination Marks 81 azimuth line was transferred to Pier to measure the azimuth of the brass peg installed by J A Major 1971 and the 1983 reference mark SOH reinstalled by Cechet 1984 measured azimuths from Pier were 1 brass peg 355 25 3 cf Major s result 355 24 9 2 Mark 50 274 14 8
67. hough it was not required after the Shutdown of the photographic seismic system was removed 24V devices were fitted with low voltage two pin plugs and power was distributed through power sockets 12V system was converted to a 6 pin Jones plug setup not ideal but the only other type of plug available The original system no doubt originated from the lack of general hardware available to Mawson geophysicists The power monitor board was removed from service for safety reasons Switchover power relay boxes were ordered so the 1 could be removed also for safety reasons 5 1 Power Supply The primary sources of power are station mains 240V 50Hz a battery 24V supply and a battery 12V supply 240V system drives most of the equipment Station power was not totally reliable and suffered from poor frequency regulation and variations supply voltage The new power house is a vast improvement on the old but still suffers from reliablity problems Station power was regulated by a Stabilac voltage stabiliser and was for atime used only as a secondary supply as backup to inverter power low voltage devices the Time Mark Unit the GED clocks 24V backup power the magnetic photographic recording lamps and the timing circuitry The remote equipment rack in the Cosray vault also has its own 12V battery supply Low voltages were supplied from standard car batteries charged by Boss charg
68. ic in prep Helicorder hot pen recorder installed for SP Z and 7 and SP N Benioff restored Vault beneath Cosray building fully concreted in readiness for movement of 5 and SP E Thermostatically controlled heating introduced to stabilise LPZ Four Teledyne Geotech seismic amplifiers AR320 installed for connection to tuo twin hot pen recorders Horizontal seismomelers and the Benioff photographic recorder disconnected Horizontal seismometers connected to visual hot pen recordevs after reinstallation in Cosray vault and conversion recorders to dual channel Appendices 2 APPENDIX P P PEN N PAPER PEM PARAMETERS Temperature coefficients Jt should be possible to calculate good approximation to the horizontal temperature coefficients given that the magnets in the QHMs have been calibrated at the Rude Skov Observatory accurately enough for absolute observations The equation of equilibrium of a QHM magnet in PEM is M C F where moment of the magnet MO moment of the magnet at 0 C C component of the field the is measuring F feedback field produced by the T torsion constant of the GiM fibre D torsion in the QHM fibre introduced during the installation M can be written as MO 1 kl t where is the QHM temperature coefficient and t is the temperature in degrees centigrade Consequently the above equation can be written as
69. ility The preliminary mean monthly field and K index values for the months of data processed based the preliminary instrument corrections and magnetograph parameters in Tables 8 and 9 are summarised in Table 10 The preliminary values of various field components over the last decade are summarised in Table 11 2 3 Photo electric Magnetograph On the author s arrival the Y PEM was not functioning The PEMs had been recording on single channel HP chart recorders The electronics in the Y PEM was recalibrated but not replaced according to the description in the manual The scale value coils of the and PEMs were connected in series with the X scale value current output 24V backup power supply was installed in the PEM controller and a faulty current monitor jack was replaced The chart recorders were d by a Linseis recorder and digital EDAS cassette recorder was installed During the alterations the was knocked while replacing the thermal cover It was reoriented he only deliberate discontinuity to the operation of the PEM that occurred following the initial changes was the relocation of the Doric thermistor from the X PEM to the Y PEM on the 17th June Digital recording began on the 20th May Mawson Magnetic Observatory There appeared to be no discontinuities the data until 13th January 1985 when a quarry blast may have caused a base line jump 2 3 1 Notes on installation and orientation
70. ing during the year The electronics room in the variometer building is not heated This caused several problems with some of the electronics which 1 only rated down to 0 In the new building it will be desirable to keep all of the electronics at above O C The temperature in the variometer building varies by 5 C between floor and instrument level and several degrees at the same level at different distances from the heaters It also varies by 3 C at the PEM location response to the thermostat cycle period In winter it is about a forty minute cycle This cycle was very apparent during the operation the Doric thermistor which was recorded on chart paper It is not however apparent on the La Cour records which leads to some degree of mistrust in the correlation between the temperature traces and the measured temperatures in the hut The new variometer building is far better insulated than the old one and heating requirements would be expected to be much less A circulating air heating system to maintain much more even temperature through the new hut was suggested The Absolute Hut is heated by a twin bar heater During winter the temperature at instrument height be 5 C and nearly out of range of the thermometers Also there is considerable temperature differential between the pier position and the bench where the magnetomers are this leads to temperature stabilisation problems better
71. line at this time was 7885 5 i e the asymptotic baseline of 7876 2 nT a decay term of 15 7 nT and an instrument correction term of 6 4 nT The Y PEM baseline was 16144 6 nT i e the asymptotic baseline of 16090 2 nT decay term of 52 7 and an instrument correction of 1 7 nT See subsection 2 3 2 Baselines for the derivation of these baselines at standard temperature The uncertainties in the X and Y baselines are equivalent to uncertainties the derived values of D of 2 1 nT and 0 47 respectively The uncertainties in the La Cour H D baselines during the above period are 2 1 and 0 5 respectively The tolerence in the scaling of La Cour mean hourly values is 0 4mm or 8 5 for and 1 0 for D Hence one may expect PEM La Cour difference of about 12 nl for and 2 for D for particular hour interval and an average difference for a large number of hours of 4 nT for H and 1 for D The temperature coefficients of the derived values of and D from the data are 49 0 nI C and 0 2 C calculated from qx temperature trace for the PEM was extremely insensitive and the actual temperature can only be estimated from spot checks taken daily at record changes The adopted temperatures and the hourly La Cour PEM differences are shown in Table 12 The average differences between the mean hourly values from the two magnetographs
72. malfunctioned early in the year depriving the clock of display clock was still usable albeit with difficulty and was not used subsequently The comparator display digits on the other clock failed at a later time This was not considered significant as connecting the radio output to the clock comparator was difficult method of performing clock corrections owing to the many spurious pips received An alternative method of comparing the clock and the time pips was used the filtered audio output of the radio and the one Control Equipment 5 2 second pulses from the clock were fed into dual channel and the time difference was measured This required the construction of a delay circuit to trigger the CRO approximately 950ms after a second mark from the GED clock so that all of the second mark and time pip could be seen whether the clock was fast or slow See Figure 7 This method allowed the observer to use judgement in detecting the start of a time pip and the quality of reception of individual pips and also to disregard spurious pips and distinguish between multiple pips on the same frequency The timemarks from the clock drove the seismic system via a relay board and the La Cour system via the same relay board and the Programmable Time Mark Unit TMU 1 The end result was to supply 12V pulses to the seismic recorders and closures to the La Cour system During the 1985 changeover the relay board and the Time Mark
73. n active field to an apparent quiet field in order to relate the circle readings of a QHM observation to a single output from multicomponent variometer Calculation of a QHM s H The formula given in a number of publications such as the QHM User s Manual Danish Meteorological Institute gives the full QHM formula as H K n 1 kl t 1ek2 H cos phi sin phi cos b where H horizontal field strength K QHM constant n number of pi rotations used kl temperature coefficient k2 QHM induction coefficient t temperature phi average n pi circle deviation from the zero pi reading b phis phi 2 1 n pi circle deviation from the zero reading phi n pi circle deviation from the zero reading alpha as usual the residual deviation tan a sin phi sin phi 2 cos phi cos phi The effect of the final term cos b is often only a few tenths of a nanotesla and can be ignored However it is not always safe to assume that the QHM is so well adjusted that the neglection of this term is justified Although the correction that arises from the term can be accounted for in comparisons when the QHM is used in same field strength as the one it is compared in the correction will vary if the field strength changes from Australia to Antarctica say In one case QHM305 the residual deviation was about 200 in Canberra and about 130 in Papua New Guinea leading to
74. nd daily calibration pulses were applied at the start and end of each SPZ chart but not the LPZ chart As far as possible the recording polarities of the seismometers were kept to the standards Up North East are all These polarities and any brief anomalies are recorded on the seismograms Complete calibrations were carried out the SPZ system the 14th October 1984 and the 21st January 1985 See Tables 18 and 19 and Figures 4 and 5 complete LPZ calibration was carried out on the 24th January 1985 See Table 20 and Figure 6 The calibrations were performed using the BWD minilab function generator and the Fluke digital multimeter to monitor the input signals The minilab frequency settings found to be very inaccurate had to be precalibrated the final signal periods were measured directly from the seimograms multimeter was used to obtain the positive and negative peak voltages by reversing the leads of the meter and the overall peak to peak voltage derived by addition attempt was made to perform the calibrations remotely from the Science Building but it was found that high frequency noise in the cable made it difficult to measure the peak current values and so the usual seismometer site calibrations performed On the departure of the author following reinstallation of all seismometers and installation of new AR320 amplifiers the entire system was uncalibrated 4 3 818 During the
75. ne during the author s absence to Neil Christie for paying meticulous attention to the quality of the output of the new power house and improving the appearance and readability of the seismic charts immensely and to the DHC foremen Mike Hartnett Danny O Reilly for doing all their power to minimise the disruption caused by the rebuilding program and for their assistance in surveying the observatory sites word of praise to Tim Sandford who operated a rock crusher and quarry only 59 meters and on occasions much less from the variometer building for never causing direct damage to the building Many thanks also to all those people and their sponsoring organisations who knowingly or otherwise contributed to BMR s inadequate supply of electronic parts and hardware Acknowledgements 5 Cechet R P 1984 Mawson Geophysical Observatory Annual Report 1983 Bureau of Mineral Resources Australia Record 1984 36 Draper and Smith Applied Regression Analysis Wiley Series in Probability and Mathematical Statistics Major J A 1971 Mawson Geophysical Observatory Annual Report 1969 Bureau of Mineral Resouces Australia Record 1957 79 Marks A S 1982 Mawson Geophysical Observatory Annual Report 1981 Bureau of Mineral Resources Australia Record 1982 28 McGregor P M Notes on the use of the QHM magnetometer in the measurement of horizontal intensity and declination Bureau of Mineral Res
76. nsation problems lengthening the time between observations and increasing scatter or dismantled and stored in insulated boxes again lengthening the time between observations but avoiding the condensation problems 3 The hut temperature could not be reduced to the external temperature even with the door open and the heating off because of the thermal absorbtion on sunny days Cloudy days were better Other Antarctic Observatories 4 Performing pairs of observations under the circumstances was worse than useless For example the last 172 observation each set was never used in any of the calculations Under these conditions where the major source of error in the 1985 comparisons this was 10 50nT is the field variation the prime concern is to reduce the time between observations with different instruments suggested alternative schedule is H172 F1023 764 7236 F1023 H172 H493 H493 H172 using only the first zero pi and n pi readings for all observations and ommitting subsequent n pi readings D505 H493 H493 D505 using only zero pi readings for QHM i e omitting the n pi and n pi readings correction for QHM torsion in D and H calculations and the estimation of the average phi value from the plus phi value in calculations can be made from knowledge of the instrument parameters determined from the accumulation of recent observatons using the particular instruments i e
77. ograph parameters in the various configurations See Figure 2 for the layout of the Seismometer Room in the Cosray Vault 4 1 Operation The horizontal seismometer photographic recording system suffered the same noise problems as previous years and required occasional adjustment to the time mark mirrors and lamp intensities the system is no longer in operation it will not be described in this report See Silberstein 1984 and Cechet 1984 for details of the system changes were made in 1984 other than essential maintenance the author s arrival the SPZ system was working satisfactorily LPZ system was unsatisfactory in many respects the 5 preamplifier was separated from its rack and attached to its own mains fed transformer power supply and hence not backed up by battery power during station power failures the calibration circuitry was disconnected the temperature compensating circuitry was disconnected and the seismometer was completely undamped This situation had persisted for some time according to previous reports following action was taken 1 The temperature compensating ciruit board was removed and RTA d Seismological Observatory 4 2 TAM5 amplifier was returned to the equipment rack and powered from the battery fed PP2 power supply 3 The output from the rack to the calibration coil was located 4 5 1K damping resistor was installed on the 24th September 1984
78. ontal field X Y t is the temperature of the variometers ts Xs Ys are arbitrarily assigned standard values for t X and Y Xs ys are arbitrarily assigned standard values for x and y d is the number of days from an arbitrarily assigned time origin The time origin was taken to be Julian day number 170 of 1984 18th June the standard temperature ts was taken to be 0 the standard values the field Xs and Ys were taken to be 8200nT and 16500nT and the standard values for the EDAS values xs and ys were taken to be 5000 although the values for null input to the EDAS were for both x and y 4991 The observations were taken over a range in the field of 250nT for X and 170nT for Y although only a few observations actually fell outside of a range of 100nT in X and 65nT in Y range in X and Y at Mawson would be expected to be about 1000nT Hence the errors in the derivation of misalignment effect the extremes of the data by an amount ten times as great as the effect on the baseline reductions The derived values of H from QHM observations used in processing the PEM data were made taking into consideration the effect of residual torsion These derivations differed from the standard La Cour Data Processing Programs by a small amount See Table 7 No instrument corrections were made In particular no correction was made for the error in observation technique while using the declinometer see Section 2 1 Absolute Instruments
79. orientation current produced no effect fibre torsion was adjusted until the quiet field output of the QHM was 300 to 400 nT above the midpoint of the instrument output 0 volts for X and a similar amount below for Y This was done as the depression caused by magnetic storms is equivalent to East and South variations to the field Care was taken to ensure that positive changes in voltages and currents corresponded to North and East variations of the field It should also be noted that for Mawson declination 63 5 West that the 0 magnet needs to be rotated west and not east as described in the manual he scale value of the analogue records was adjusted to be as near to 15 nT mm as possible In future installations it would be desirable to countersink a hole in the instrument pier for one of the levelling feet of the unit so that it can be repositioned if knocked One of the other feet can be marked precisely so that it too can be repositioned to achieve the same orientation or differ by exactly measurable angle should reorientation be desirable 2 3 2 Baselines attempt was made to reduce the observations taken during the year to the X and Y baselines Only observations from the 17th June 1984 until the 13th January 1985 were considered as there appears to be discontinuities the data outside of those times Both the X and Y PEMs exhibited relaxation of the QHM fibres in the form of
80. ound that the most suitable joining method employed Scotchlock crimping connectors In summer the join should be encased in epoxy resin but in winter when it is difficult to prevent the resin from freezing the join should be covered with heavy duty heat shrink tubing The shield material cannot be soldered and it was suggested that automotive coolant system hose clamps be used to make physical and electrical connections in the join Control Equipment CHAPTER 6 BUILDINGS AND BUILDING MAINTENANCE The buildings used in the operation of the BMR observatories are 1 Magnetic Absolute Building 2 Magnetic Variometer Building 3 New Magnetic Variometer Building 4 Micropulsations Building or Variometer Power Supply Building 5 Old Seismic Vault 6 Cosray Building 7 Science Building or Wombat he Magnetic Absolute Building is blasted by snow and ice particles carried by the prevailing winds It is in moderately good condition only maintenance carried out was painting the windward wall with one coat of undercoat and two layers of silver topcoat addition another hole with internal and external sliding covers was made in the southern wall to observe a new mark from Pier A The Magnetic Variometer Building will cease to be used some time 1985 No problems were encountered with this building other than an occasional buildup of drift around the instrument piers during blizzards New Magnetic Variometer Building w
81. ources Australia Record 1967 140 Oldham W H 1957 Magnetic Work at Mawson Antarctica 1955 56 Bureau of Mineral Resources Australia Record 1957 79 QHM The Quartz Horizontal Force Magnetoneter User Manual Danish Meteorological Institute DK 2100 Copenhagen February 1978 Silberstein R P 1984 Mawson Geophysical Observatory Annual Report 1982 Bureau of Mineral Resources Australia Record 1984 35 Wolter P J 1981 Mawson Geophysical Observatory Annual Report 1976 Bureau of Mineral Resources Australia Record 1981 7 References APPENDIX HISTORY OF INSTRUMENTATION UP TO 1985 A brief summary of the development of Mawson Geophysical Observatory in terms of instrumentation until 1985 is presented below May Jul Jan Dec Sep Feb Dec Mar Aug Jul Jul May Jul 1955 1955 1957 1961 1967 1968 1975 1975 1981 1982 1983 1983 1984 1956 1960 Geomagnetic Absolute instruments used for regular observations of D amp 7 Oldham 1957 Continuous recording commenced three component normal La Cour magnetograph Oldham 1957 Bar fluxmeter magnetograph installed Pinn 1961 Three component insensitive La Cour magnetograph installed and recording commenced Merrick 1961 Bar fluxmeter magnetograph withdrawn Dent 1971 Insensitive La Cour magnetograph converted to medium sensitivity and renamed normal magnetograph The normal
82. puts at the zero readings and calculating the relevant delta D calculations were virtually identical and the D calculations differed only in the term involving the residual torsion angle alpha value of alpha calculated by the above method displayed a reduced scatter when compared to the usual processing method scatter reduced from 0 9 to 0 5 equivalent to a reduction in the scatter the derived X and Y values of about The improvement would be expected to be better with better variometer control corrections outlined in this appendix are equivalent insofaras the calculation of alpha to the correction given in the User s Manual Danish Meteorological Institute for the calculation of alpha in a varying field Another application of this processing technique would be to investigate the importance of observation schedules referred to by McGregor 1967 by observing the minute by minute creep in the QHM fibre the torsioned position after correcting for all field variations The time period of the creep displayed by QHMs installed in PEMs is of the order of hundreds days which indicates that the creep during an observation should be unimportant See Section 2 3 Baselines This is inconsistent with McGregor s report and the assumption in this report that the fibre relaxation decays exponentially Appendices D 4 APPENDIX E USING THE QHM IN ODD PI MODE QHM
83. rcuitry was not capable of driving the relays in the variometer building For about a month around July while the Advance Electronic Inverter was running the entire recording system was virtually unaffected by station power failures While relying on station power however there were many short periods of data loss and the occasional day when the chart would not last for 24 hours as the station power frequency was exceptionally high 2 2 1 Parallax Tests Parallax tests performed shortly before after every set of absolute observations for baseline determination and instrument comparison This was done to allow the event marks for the observations to be accurately transferred to the data traces using a parallel rule There isa small parallax between both the H and Z traces and their respective timemark traces both cases the data trace is minute of time to the left of the corresponding timemark i e the parallax corrections are 11 0 minutes As mentioned above there is no D timemark trace Either the 7 timemarks be used D trace 15 five minutes to the right the corresponding H timemark and eight minutes to the right of the corresponding Z timemark i e the parallax corrections for the D trace are 5 0 minutes using the H timemarks and 8 0 minutes using the Z timemarks Mawson Magnetic Observatory gt 2 2 2 Orientation Tests Orientation tests were carried out on the H and D v
84. roughout the year Unfortunately the observation procedure for using declinometers was incorrect The base of the declinometer was left on the circle during the mark siting causing refraction errors This led to a declination correction of 1 2 WEST This error technique relates to all D baseline reductions and preliminary mean values from February 1984 to January 1985 inclusive and to the February 1984 D comparisons In January 1985 mark sitings were made using the correct and incorrect technique to determine the above mentioned correction Mawson Magnetic Observatory 2 2 18 Cour Magnetograph The La Cour was operated continuously from 151 February 1984 until 3151 January 1985 except for the following periods of record loss February 1984 17th 09 24 UT 18th 00 03 UT March 1984 15th 01 02 UT April 1984 015 03 06 UT 12 24 UI 02nd 00 06 UT June 1984 llth 20 24 UT 12th 00 09 UT 11 13 UT This was total of 55 hours 0 6 the total recording period Data quality was reduced on several other occasions but the data was recoverable he primary reasons for data loss and degradation of data quality were failure of the 12V supply to the variometer building 2 jammed drum motor gears 3 failure of station power supply 4 loose intermittent connections in the power supply and timing circuits and failures in the timing electronics in the variometer building 5 unable to perform chart change because of blizzards
85. s are used in 2 pi 3 pi modes making the assumption that l pi 1 pi 2 pi 2 pi etc While it is obvious that 2 pi 2 pi it is not quite so obvious that 1 pi 1 pi What this means 15 that it may not be true that the front and back mirrors of QHM are exactly parallel For instruments that are used in odd pi modes it is worthwhile confirming that the mirrors are close enough to parallel or if not determining the error course it may not be possible to compare some 1 pi instruments to the 2 pi mode unless they are taken to a place of high field by natural or artificial means so Antarctic QHMs should be tested in Australia Let m an odd integer e the angle between the back and front mirrors of the QHM the residual deviation angle alpha apparent deviation of the magnet in the m pi position from the zero position phi apparent deviation of Lhe magnet in the m pi position from the zero position phi average of phi and phi actual deviation of the magnet in the m pi position from the zero position phi actual deviation of the magnet in the m pi position from the zero position phi average of phi and phi M moment of the QHM magnet horizontal field strength fibre torsion constant residual torsion in the fibre Then phi phi e phi 1 phi phis phi 2e phi phi phi phi phi phi
86. ted temperatures for the PEM were taken from spot readings during chart changes and are not fully indicative of the temperature variations Hence some temperature correction errors will exist data The temperatures were 2 C the 4th 1 C on the 5th 1 5 C on the 6th and 0 5 C on the 7th The differences are in the sense La Cour value PEM value eastwards declinations reckoned positive Tables 13 INTERCOMPARISONS OF MAGNETOMETERS Davis January 1984 Date Instrument Instrument B Difference Jan 15 1984 BMZ 121 BMZ 115 358 5 nT Values are given with no instrument corrections applied Thermometer corrections were not available and assumed to be zero BMZ 121 was used with long range magnet set at division 16 115 was used with magnet set at division 17 however the BMZ constants only give divisions 16 and 18 Cubic interpolation was used to estimate the nominal division 17 calibration 14 INTERCOMPARISONS OF MAGNETOMETERS Casey March 1985 Date Instrument Instrument B Difference A B at 9600 Mar 13 14 85 172 QHM 493 40 8 13 3 nT 0 00425H 13 14 85 172 PPM 1023 BMZ 236 105 6 44 7 nT 13 14 85 64 BMZ 236 77 8 33 7 nT 15 85 640505 QHM 493 91 6 6 5 508813 alpha 15 8 5 9 collimation angle 75 8 5 7 The values of the residual torsion deviation alpha for these observations were QHM 17
87. th December 1984 Two sets of comparisons sandwiching QHM302 H and D obs between Dec332 and QHM300 were made The D comparisons showed that QHM302 had a correction of 26 0 i e eastwards correction relative to the standard 630332 This correction was made up of collimation correction of 26 4 and an alpha residual torsion Mawson Magnetic Observatory ma correction of 0 4 The H comparisons showed that QHM302 had a correction of 4 4nT compared to the annual average of 4 9nT relative to the standard QHM300 2 8 Data Communications Data was frequently transmitted to Canberra via handwritten telexes passed to the radio operators but whenever the or IPS computing facilities were available the telex tapes were generated from computer files This reduced the workload on the operators and provided the opportunity to check the final telexed data immediately before transmission to remove transcription errors few computer programs would have been useful perform standard report processing calculating K indices from and D indices for example and eliminate other sources of errors in the monthly reports Mawson Magnetic Observatory 4 CHAPTER 3 OTHER ANTARCTIC OBSERVATORIES 3 1 Davis BMZ comparisons were carried on the voyage to Mawson in January 1984 with the assistance of Warwick Williams observing conditions were far from ideal and the observations were necessarily rushed du
88. the PEM EDAS 6 OBSERVED BASELINE VALUES FOR LA COUR MAGNETOGRAPH 1984 Date Baseline Remarks Horizontal Intensity 1984 Feb 01 0000UT Mar 10 180007 new observer 17435 0nT 3 3nT QHM 300 17432 7nT 3 5 QHM 301 17433 2nT 3 4nT QHM 302 Mar 10 1800UT May 07 0900UT unknown 17428 1nT 2 3nT QHM 300 17425 5nT 1 8 QHM 301 17433 2 1 4 2 4nT 302 07 0900UT Nov 19 200007 unknown 17421 5nT 2 1nT QHM 300 17419 9nT 1 8nT QHM 301 17426 6nT 1 9nT QHM 302 Nov 19 2000UT Jan 03 1330UT Tz baseline change 17421 9nT 3 6nT QHM 300 17420 8nT 2 6nT 301 17426 7nT 3 6nT QHM 302 1985 Jan 03 1330UT Jan 12 1320UT quarry blast 17418 2nT QHM 300 17416 9nT QHM 301 17424 0nT QHM 302 Jan 12 1320UT Jan 31 2400UT quarry blast 17396 5nT 1 9nT QHM 300 17395 0nT 1 3nT QHM 301 17402 6nT 3 3nT QHM 302 Declination 1984 Feb 01 0000UT May 18 1800UT 61 44 3 0 5 new observer 18 1800UT Nov 19 0900UT 61 43 3 0 5 unknown Nov 19 0900UT Jan 03 1330UT 61 42 7 0 5 optics adjustment 1985 Jan 03 1330UT Jan 14 1020UT 61 39 8 0 5 quarry blast Jan 14 102007 Jan 31 2400UT 61 40 4 0 4 quarry blast Tables Vertical Intensity 1984 Feb 01 0000UT Nov 19 2000UT 46428 7nT 3 0nT new observer Nov 19 2000UT Jan 03 1330UT 46192 2nT 1 9nT optics adjustment 1985 Jan 03 1330UT Jan 12 1320UT 46159 2nT 4 1nT
89. uced along the transmission path from radio transmissions etc and reduce the requirements on the cable connecting the buildings The Hewlett Packard Integral Personal Computer operates under the UNIX Mawson Magnetic Observatory multitasking operating system and provides graphics capability it is an example of a microcomputer capable of performing the tasks required at the observatory similar tasks in field surveys and many other tasks in the office at Other possible computers are Convergent Technology machines using the CTOS operating system and the IBM Personal Computer using Concurrent DOS 2 4 Comparison of La Cour PEM Data The facilities for reading the EDAS cassettes at Canberra were occupied reading the cassettes from other observatories As the PEM not the primary magnetometer during 1984 at Mawson only small part of the data was processed The lack of accurate temperature information on the PEM was a source of some uncertainty as to the meaning of the magnetic traces but nevertheless a comparison between the mean hourly values of the PEM and La Cour variometers for certain periods was attempted Cassette MAW 84 008 was submitted to the computer room to be copied to disc After several failed attempts to read the cassette three of the eleven days data on the cassette were transferred to disc The data began on 4th August 1985 at 1300UT day 217 and ended on 7th August 1985 at 2000UT day 220 The X PEM base
90. ven at TAM5 set to 96db gain AR320 Seismometer Free Period Damping Resistor 0 015 mm mg 2 29 mm mA 1 50 N A Weight lift tests Current pulse tests Motor Constant G Magnification Conversion Tables masses used l2db attenuation 0 1 10Hz passband 30db attenuation 0 96 secs from Oct 84 results 386 ohms currents used 3mA 6mA approx p p value 100mg 1000mg currents used Attenuation 0 db 6 db 0 db 1 0 504 6 db 1 98 1 12 3 92 1 98 18 db 7 89 3 98 AR320 Attenuation 18 db 24 db 18 db 1 0 518 24 1 93 1 30 3 79 1 96 36 7 89 4 09 120 18db 0 255 0 127 0 506 0 251 1 0 497 2 01 1 30db 36db 0 264 0 127 0 510 0 245 1 0 480 2 08 1 Tables 1 7 SEISMOGRAPH CALIBRATION January 1985 Magnification Period secs 5 90 440 7 93 380 8 97 373 10 06 355 11 78 300 11 87 301 11 95 300 12 23 288 12 98 254 13 33 232 14 62 177 15 60 137 17 08 100 18 07 81 19 44 62 20 76 48 21 85 41 24 30 27 27 27 18 30 24 14 35 07 8 6 39 76 5 4 49 80 2 8 62 53 1 3 Magnifications are given at 5 set to 72db gain AR320 Seismometer Free Period Damping Resistor Weight lift tests 613 mm mg Current pulse tests 10 88 mm mA Motor Constant G 0 21 N A The pivot to weight lift point for the tests was 370mm pivot to centre of gravity of the mass is 308mm see seismometer mass used in calculations was 6 9 kg This
91. where in particular 5 variety of cables within the Cosray and Science buildings which were not in use removal of these cables cleared up a great deal confusion about how data got into and control out of the Science Building Very little of the cable was retrievable in sufficient lengths to be reusable most the plastic covering of the shielded cable had been cracked by the cold and some cables had been cut by vehicles In addition the pyrotanex cable from the Science Building to the 01 Seismic Vault was not in use and was offered to the Bureau of Meteorology for their use 15 left the following cables other than station power services which are of relevance to BMR for long term usage 1 the 10 twisted pair shielded cable from the Cosray vault to the Science building carrying seismic information control signals This cable was damaged near the Pump House and had a new section spliced into it It was laid in February 1984 2 the 10 twisted pair shielded cable from the New Variometer Building to the Science Building carrying magnetic information and control signals This cable was partially laid in February 1985 during changeover and completed during 1985 by Peta Kelsey En the cable carrying 12V from the Cosrologists office to the Cosray vault for short term usage 4 the 7 core pyrotanex cable from the Science Building to the Old Variometer Building carrying 240V for the recor
92. with the vertical system and suffered the same radio interference noise problem noise problem occurred only two of the four signals and occurred on only one signal on each recorder one signal on each of the two AR320 racks and signal of the two horizontals installed in the same rack using the same PP2 power supply in short the problem was traceable to no specific common component between pair of seismic Signals During the initial power up of the new AR320 amplifiers for the Horizontals the negative voltage regulators in the AR320s vapourized it was disappointing that the equipment had never been tested before being sent to Mawson and apparently not since its construction in the factory The general lack of detailed circuit descriptions and lack of rack building hardware at the observatory seems to be the cause of the persistence of the untidy and less than fully reliable system Seismological Observatory 4 2 Calibrations The polarity of the horizontal system was checked soon after arrival in February 1984 and found to be South is up East is up Daily calibration pulses were applied at the beginning and end of each chart No complete calibration was performed before the seismometers were moved to the Cosray vault The last calibration of the seismometers appears to have been in 1982 see Silberstein 1984 polarity of the vertical seismometers was checked whenever system connections were altered a

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