A Course in Geophysical Image Processing with Seismic Unix
Contents
1. 4 3 1 What are the trace header fieldsssukeyword 4 5 2 Types of data formats lt 2 44 5 e564 04645844 5 AA Concluding Remarks s w s s s cos eo seas omen ESB ES Q w W Lab Activity 4 Migration Imaging as depth conversion 5 1 Imaging as the solution to an inverse problem 5 2 Inverse scattering imaging as time to depth conversion 5 2 1 Migration as a mapping of data from time to space 5 2 2 Migration as focusing followed by depth conversion 5 3 Time to depth with suttoz depth to time with suztot 5 4 Time to depth conversion of a test pattern X 5 4 1 How time depth and depth time conversion works 54 2 How to calculate the depths Z1 Z2 and Z3 5 5 Sonar and Radar bad header values and incomplete information 5 6 The sonar data 442 640584 004 be eee de ea oecw dats 5 7 Homework Problem 2 Time to depth conversion of the sonar su and the radar su data Due Thursday 10 September 2015 and Tuesday 15 September 2015 for the respective sections 0 2 4 5 8 Comneludine Remarks oo ao ceceo u u s owe ee s G ee WO a ee awe eG 5 8 1 The sonar seismic analogy 208 Zero offset aka poststack migration 6 1 Migration as reverse time propagation 2 4 6 2 Lab Activity 5 Hagedoorn s graphical migration 6 3 Migration as a Diffraction stack 22 ad 4m2. exist physically on another machine named isengard but are remotely mounted as to appear to be on this machine The second column from the left shows the total space on the device the third column shows the amount of space used while the fourth shows the amount available the fifth column shows the usage as a percentage of space used Finally the far right column shows the directory where these devices are mounted In Unix like environments devices are mounted in such a way that they appear to be files or directories Under Unix like operating systems the user sees only a directory tree and not individual hardware devices If you try editing files in some of these other directories you will find that you likely may not have permission to read write or modify the contents of many those directo ries Unix is a multi user environment meaning that from an early day the notion of 19 20 protecting users from each other and from themselves as well as protecting the operating system from the users has been a priority In none of these examples have we used a browser yet there are browsers available on most Unix systems There is no fundamental problem with using a browser with the exception that you have to take your hands off the keyboard to use the mouse The browser will not tell you where you are located within a terminal window If you must use a browser use column view rather than icon view as we will have man
3. to see what the system says about these commands For example man ls LS 1 User Commands LS 1 NAME ls list directory contents 24 SYNOPSI 25 8 ig OPTION FILE DESCRIPTION MORE List information about the FILEs the current directory by default Sort entries alphabetically if none of cftuvSUX nor sort Mandatory arguments to long options are mandatory for short options too a all do not ignore entries starting with A almost all do not list implied and The item at the bottom that says MORE indicates that the page continues To see the rest page for Most of the man page for Is is viewed by hitting the space bar View the Unix man each of the Unix commands you have used so far Unix commands have options such as the Is a which allowed you to see files beginning with dot or Is l which shows the long listing of programs Remember to view the Unix man pages of each new Unix command as it is presented References Sobell M 2010 A practical guide to Linux commands editors and shell program ming Pearson Education Inc Boston MA 25 Chapter 2 Lab Activity 1 Getting started with Unix and SU Any program that has executable permissions and which appears on the users PATH may be run by simply typing its name on the commandline For example if you have set your path correctly you should be able to do the following suplane
4. 0 10 0 15 0 25 Figure 3 1 Image of sonar su data no perc Only the largest amplitudes are visible 36 37 200 400 0 05 0 10 0 15 0 25 Figure 3 2 Image of sonar su data with perc 99 Clipping the top 1 percentile of amplitudes brings up the lower amplitude amplitudes of the plot 37 38 3 3 Legend making grayscale values scientifically meaningful To be scientifically useful which is to say quantitative we need to be able to translate shades of gray into numerical values This is done via a gray scale or legend A legend is a scale or other device that allows us to see the meanings of the graphical convention used on a plot Try suximage lt sonar su legend 1 amp This will show a grayscale bar There are a number of colorscales available Place the mouse cursor on the plot and press h you will see that further pressings of h will re plot the data in a different colorscale Now press r a few times The h scales are scales in hue and the r scales are in red green blue rgb It is important to see that the brightest part of each scale is chosen to emphasize a different amplitude With colormapping some parts of the plot may be emphasized at the expense of other parts The issue of colormaps often is one of selecting the location of the bright part of the colorbar versus darker colors Even perfectly processed data may be rendered unin
5. Figure 2 3 32 JSHASL ue q PALU oso 1d ox puguuutoo Y JO PUD MP IE NYNLTA SSA ays wosf yxy u gol punossasof auinsay u qol punoss yong aumnsay punossyovg ut pupunuo 3 uny u qof punossyong pu dsn ssao04d JUadANI pu dsn u ssav0id anowlay SIDIS SNIDIS ss 204d JU u qof my sqof fo 151 It d spuogas u sof d indjno u 49s aunsay 8U1 04IS U234IS dog S ss 5oad Jdnssaquy uopdnsq wxo u By 4 3q PUDUUWOI u dos x NAD u6 IA sd lu LLL sqof u d ls bn x SMO x AID puguruoo JO1JUOD SS9D01q AapIAUOD ISD g 1fo od Aapiduiod Z SUDAJAO J OIL O L4 S404 AOL APO J YOOYD fui dapiduioo J zf He J sa uondtr s I pugunruo9 J j dw09 f Jo pu nding f f fo SunnauS q mdjnO fpe saquasaffip f sisr zf Hp ujd yogpu Joy souy smdmo J aud daag Jof aowa ajajaq fuu zf sp f opf aumuay Z xu saad auy u ogui f ids J lu yds Juos amp ponqoydiy fuos gom pf apf Kdo g if do sajf ow aapduioy g I duo f fo pouu uotj9 oid Sunuo J pout pouiuo f ona zf Lf s mu m uoo geg yw U224IS KG sJu luo2 Af ISTT J aow aif Jo siu Juo2 IST J wo JUNOD ADYD 32 paom ur Sm AONPa D I I pe A0JIp u 42s nf SODU H soewe AOJID u 42s nf 1A H A uordri2s q pugururo uonejndiue 9l 4 puomi auyugQ 4of Kjua Ipninut XIN gpu Jo uoypoyfiyou Jupysuy 4AISN Of JDU Puas jpuiusal Suns dorg SO uorssas Dunu4 AD A4 p
6. Homework 9 Velocity analysis for stack Due Thurs 12 Nov 2015 before 9 00am and Tuesday 10 November 2015 This assignment is paired with Homework 10 in the next chapter so be aware of His as oe Oe ae Pe eae y eS gt n 219 12 1 Other velocity les on 8 eae ees RRR RR Re RS Ee RR ES 220 12 1 1 Velocity analysis with constant velocity CV stacks 220 12 2 Dip Moveout DMO lt 2 x k me wake ea ele ee 2 eee eS 222 12 2 1 Implementing DMO n ne dee eee eee ew EE 222 12 3 Concluding Remarks 252 6058 ed 4 oe de hee eee SE RE ES 223 13 Velocity models and horizon picking 224 13 1 Horizon picking and smooth model building 225 13 2 Migration velocity 68t8 2 6 6 4 lt 4 g 6 6 084 288 9 ee eo i ee eS 226 13 2 1 Homework 10 Build a velocity model and perform Gaussian Beam Migration Due 12 Nov 2015 for both sections 227 13 3 Conel uding remarks s s s o s ses oa ede da S Qua w eb W W W See w N 227 14 Prestack Migration 228 14 1 Prestack Stolt migration aooaa a ee ee es e e 228 14 2 Prestack Depth Migration aooaa aa o 229 14 3 Concluding remarks ___ _ a ae Bah eae Ge o 229 List of Figures dl 2 1 2 2 2 3 2 4 3 1 3 2 3 3 3 4 3 5 3 6 3 7 5 1 5 2 A quick reference for the vi editor 0 0 0 0 008 The suplane test pattern 2 22 2008 a The suplane test pattern b the Fourier transform time to frequ
7. amp oS ok ee ek 6 4 Migration asa mathematical mapping 4 6 5 Concluding Remiarke 44 244 82 4 creata ngar eet ee Q s Lab Activity 6 Several types of migration 7 1 Different types of velocity 2 8 26 c0 ee 4 Sede eee e e eS 7 1 1 Velocity conversion Upms t to Vint t 2 2 ee T2 St ltori f k smpgkraliom s e a a ed ha HA Ge amp Be wt ee oe N 7 2 1 Stolt migration of the Simple model data 7 3 Gazdag or Phase shift migration 4 4 lt 2 wad ee ea eee wees o 7 4 Claerbout s finite difference migration 0 7 5 Ristow and Ruhl s Fourier finite difference migration 96 76 Stoffa s split step migration 4042426252 046254 0 er e ada 97 7 7 Gazdag s Phase shift Plus Interpolation migration 98 Ge Lab Actiwity 7 Shell scripts 2442284 248 a u k a ka s Race wa 99 7 9 Homework 3 Due 17 Sept 2015 Thursday session and 22 Sept 2015 Tuesday Session 2 h 4 2 backs od eb ae Ge SP ee de ee Edu 101 GO TAG oe 2 Bh a ee ee ee a ee sa 101 7 10 Lab Activity 8 Kirchhoff Migration of Zero offset data 102 7 11 Spatial aliasing 2k eek bee eed be SOR eee Oe eee eee de be 105 7 11 1 Interpreting the result 1 44 4 464 Bee eee eee ee 105 7 11 2 Recognizing spatial aliasing of data in the space time domain 107 7 11 3 Recognizing spatial aliasing in the f k domain 107 7 11 4 Remedies for spatial aliasing 2 64
8. data plus simulated water bottom multiples in the Radon domain c Synthetic data plus 10 water bottom multiples plus select pegleg multiples in the Radon domain 155 10 8 CMP 265 NMO corrected with vnmo 1500 displayed in the Radon trans form t p domain Compare this figure with Figure 10 2 The repetition indicates Mu ltipl s e sso a wad pama Ree Shee bad ween da 158 10 9 CDP 265 NMO corrected with the velocity function vamo 1500 1800 2300 tnmo 0 0 1 0 2 0 but with no stretch mute parameter applied NMO stretch artefacts appear in the long offset shallow portion of the section 10 10An average over all of the shots showing direct arrivals head waves wide angle reflections and a curve along with muting may be applied to elimi nate these waves o ooo a a 11 1 Example of a far field airgun source signature 11 2 a Amplitude spectra of the traces in CMP 265 b Amplitude spectra after filtering eor sordo s dbs Dede Q ate R e oa QON 2 G we 11 3 a Original fake data b fake data with spectral whitening applied Note that spectral whitening makes the random background noise bigger 11 4 Deterministic decon of CDP 265 using the farfield airgun signature esti mate rom Fig ILL sree sos eee Pee ee Ree RRM EE ER SE de QU a 11 5 a Autocorrelation waveforms of the fake su data b Autocorrelation wave forms of the same data after predictive spiking decon 10 163 Preface I started
9. each successive semester I have gathered more examples and figured out how to apply more types of processing techniques to the data My vision of the material is that we are replicating the seismic processors base ex perience such as a professional might have obtained in the petroleum industry in the late 1970s The idea is not to train students in a particular routine of processing but to teach them how to think like geophysicists Because seismic processing techniques are not exclusively used on petroleum industry data the title of Geophysical Image Processing was chosen 11 Chapter 1 Seismic Processing Lab Preliminary issues 1 1 Motivation for the lab In the lecture portion of the course GPGN452 561 now GPGN461 561 Advanced Seis mic Methods Seismic Processing the student is given a word picture and chalkboard introduction of the process of seismic data acquisition and the application of a myriad of processing steps for converting raw seismic data into a scientifically useful picture of the earth s subsurface This lab is designed to provide students with practical hands on experience in the reality of applying seismic processing techniques to synthetic and real data The course however is not a training course in seismic processing as one might get in an industrial setting Rather than training a student to use a particular collection of software tools we believe that it is better that the student cultivat
10. environment 15 16 1 6 Setting the working environment Each of these programs have a specific syntax which can be quite complicated Each is a language that allows the user to write programs called shell scripts Thus Unix like systems have scripting languages as their basic interface environment This endows Unix like operating systems with vastly more flexibility and power than other operating systems you may have encountered only as point and click environments Even those environments may have a shell command structure that the user is protected from by a windowed environment Why have such a structure The answer is that point and click is not enough The expert user needs to be able provide more complicated instructions to the computer and the shell provides the languge of those instructions With more flexibility and power there comes more complexity It is possible to perform many configuration changes and personalizations to your working environment which can enhance your user experience For these notes we concentrate only on enough of these to allow you to work effectively on the examples in the text 1 7 Choice of editor To edit files on a Unix like system the user must adopt an editor The traditional Unix editor is vi or one of its non proprietary clones vim vi improved gvim or elvis The vi environment has a steep learning curve making it often unpopular among beginners If a person is envisioning worki
11. no NMO correction b CV Stack vnmo 1500 c CV 93 106 108 110 112 113 126 128 Stack vnmo 2300 d Brute Stack vnmo 1500 1800 2300 tnmo 0 0 1 0 3 0 141 10 1 Semblance plot of CDP 265 The white dashed line indicates a possible location for the NMO velocity curve Water bottom multiples are seen on the left side of the plot Multiples of strong reflectors shadow the brightest arrivals on the NMO velocity curve 2 204 10 2 CMP 265 NMO corrected with vamo 1500 Arrivals that we want to keep curve up wheres multiple energy is horizontal or curves down 10 3 a Suplane data b its Radon transform Note that a linear Radon trans form has isolated the three dipping lines as three points in the 7 p do main Note that the fact that these lines terminate sharply causes 4 tails on each point in the Radon domain o oaoa a a a 10 4 The suplane test pattern data with the steepest dipping arrival surgically removed in the Radon domain eee 10 5 a Synthetic data similar to CDP 265 b Synthetic data plus simulated water bottom multiples c Synthetic data plus water bottom multiples plus select pegleg multiples 2 0 0 eee ee 10 6 a Synthetic data similar to CDP 265 b Synthetic data plus simulated water bottom multiples c Synthetic data plus water bottom multiples plus select pegleg multiples 2 0 0 eee ee 10 7 a Synthetic data in the Radon domain b Synthetic
12. pue 9 gqoO vur passoy ore NOK UDYM UA S LJ DULY NOK duupx 104 ssadoe UBD NOA Jey SULJU LUDISAS JL PLYS SIUL Iojutza opl ny N L IU I 1S opl n N Atu aqua prom y A1O IALIP oJurzq4 SIY o A1OJOALIP ONS SIY WOY A LJ AOU O paguem BOC uuor Ji durex 10 4 SAY u wq q syur orfoquuAs oyeur O s Adoo sayy IAOU OJ Spugututo2 xtur ATeUTpPJO Y sn UBD NOA PAS o ui p 330 AT EMoL s ys YSNOY UDAd S Y OJUrZA JOY 9S YS SA JOY SISI IYS UJM MON ojuiza iqqe3J n N po 21Q US plnoA ays UNOD OJUrZA JOY UO L 4 B JOS O SJUBA pUe S uo JUNODW 1 y OJU PASSO s yqqey LAssS f Ji dupx 104 IUDUAISN 10 utpuu Sn UMO INO n nsqns pug 0L S NOA sg ysnf uonezeydeo y asn NOA ans og dS 2uupua sim u po oJurz tupua4 snm N PO I991S 21upua snm N po PUIZ AWIDUAASNYTYN Po MeqOO aupusasny nyN po PWOAYD aluDUAASN TYN p9 swaysAs 19470 Aue woy AlOJIALIP Wyss AUB o JIS o ISN 0 SPUBLILUOD OYJ WB MH SOO y Jo Aue uo s uJ ino o Jad upo NOA OU p 88o ae NOA si nduioo asay JO YOIYM syeu ON sjunooog dary NO YSIYA UO S SOY XIUN VU IY 10 POLUBU S9LIO IALIP ut SIP IUO uo Ajpear que s u anod yeyy SULU PYL SHN 4 A4 S A l4 MONN A UO p ols I qS SUAV LS pur ojurzy PAS UZ 9 eqoO woy siayndwios xiur YU SLIN A UO Pads sA SOI SAN YUM BuntdoAA ity References Ivers 31 UNIX Quick Reference card p1 From the Un
13. sonar su data with perc 99 and legend 1 39 39 40 Figure 3 4 Comparison of the default hsv0 hsv2 and hsv7 colormaps Rendering these plots in grayscales emphasizes the location of the bright spot in the colorbar 40 200 400 0 05 0 10 Figure 3 5 Image of sonar su data with perc 99 and legend 1 41 41 42 You may find perc 99 to be useful You may find that you have to apply an RMS balancing to make the data look a bit more uniform sunormalize norm balmed lt sonar su sunormalize norm rms suximage legend 1 sunormalize norm balmed lt sonar su sunormalize norm rms suximage legend 1 perc 99 Again these commands are written as one long line and are broken here to fit on the page You may zoom in on regions of the plot you find interesting If you put both the median normalized and simple perc 99 files on the screen side by side there are differences but these may not be striking differences The program suximage has a feature that the user may change colormaps by pressing the h key or the r key Try this and you will see that the selection of the colormap can make a considerable difference in the appearance of the image Even with the same data the colormap For example in Figure 3 7 we see the result of applying median balancing We might consider applying sunormalize directly to the seismic data suximage lt seismic su wbox 250 hbox 600 cmap hsv4 clip 3 tit
14. suxwigb amp this symbol the ampersand indicates that the program is being run in background the pipe symbol The commandline itself is the interactive prompt that the shell program is providing so that you can supply input The proper input for a commandline is an executable file which may be a compiled program or a Unix shell script The command prompt is saying Type program name here Try running this command with and without the ampersand amp If you run suplane suxwigb The plot comes up but you have to kill the plot window before you can get your com mandline back whereas suplane suxwigb amp allows you to have the plot on the screen and have the commandline To make the plot better we may add some axis labeling suplane suxwigb title suplane test pattern labell time s label2 trace number amp Here the command is broken across a line so it will fit this page of this book On your screen it would be typed as one long line 26 time s 27 trace number 10 20 30 0 05 0 10 0 15 0 20 0 25 suplane test pattern Figure 2 1 The suplane test pattern 27 28 to see a test pattern consisting of three intersecting lines in the form of seismic traces The data consist of seismic traces with only single values that are nonzero This is variable area display in which each place where the trace is positive valued is shaded black See Figure 2 1 Equivalently
15. writing these notes in 2005 to aid in the teaching of a seismic processing lab that is part of the courses Seismic Processing GPGN452 later redesignated GPGN461 and Advanced Seismic Methods GPGN561 in the Department of Geophysics Colorado School of Mines Golden CO In October of 2005 Geophysics Department chairman Terry Young asked me if I would be willing to help teach the Seismic Processing Lab This was the year following Ken Larner s retirement Terry was teaching the lecture but decided that the students should have a practical problem to work on The choice was between data collected in the Geophysics Field Camp the previous summer or the an industry dataset that was acquired near the Viking Graben in the North Sea The latter dataset was brought by Terry from Carnegie Mellon University We chose the latter and decided that the students should produce as their final project a poster presentation similar to those seen at the SEG annual meeting Terry seemed to think that we could just hand the students the SU User s Manual and the data and let them have at it I felt that more needed to be done to instruct students in the subject of seismic processing while simultaneously introducing them to the topics of navigating the Unix operating system performing some simple shell language programming and of course using Seismic Unx In the years that have elapsed my understanding of the subject of seismic processing has continued to grow In
16. 11 7 1 Spiking Deconvolution in SU a aaa So cue wo 196 11 7 2 Multiple suppression by Wiener filtering Gapped prediction error HTN 2 z a Sup he ee SRR eee S US EES EG 199 11 7 3 Applying gapped decon in SU supef 201 11 8 What else did predictive decon do to our data 203 11 8 1 Deconvolution in the Radon domain 204 119 FX D66000 es Lok a a ee bh 8 Be ee Ch ee a Chee a eee eae ee 204 11 10Lab Activity 20 Wavelet shaping 12464 40400824 8 4 S 204 11 11Advanced gaining operations o oo o a a 0200000 eee 206 11 11 1 Correcting for differing source strengths 207 11 11 2 Correcting for differing receiver gains 207 11 12Filling in missing shots ewe ae eS Go Boe ek eR Rate Ee Ss 208 11 13Muting NMO corrected data 2 4 24 fe ee ee ee es 210 11 14Ghost reflections 2244245 4 4 a a s bo 648 bo 6 eee ee HO 210 11 15Surface related multiple elimination 211 11 15 1 The auto convolution model of multiples 2 211 11 16Homework Assignment 8 Due Thursday 5 Nov before 9 00am and Tues day Noy 20a e a s sached babe k S a mO E amp oe u euii oeat 211 11 16 1 How are we doing on multiple suppression and NMO Stack 213 11 17Concluding Remarks _ _ _ bo eed we OS we eS 213 12 Velocity Analysis on more CDP gathers and Dip Move Out 214 12 03 Applying migration s s isone sa a ass BAG ee de age pa 218 12 0 2
17. 6444 a beehs amp 109 7 12 Concluding Remarks 6 e4 44 4446 244 oe Paw ae ee ew Be Hs 114 Zero offset v t and v z z migration of real data Lab Activity 9 115 8 1 Stolt and Phaseshift v t migrations i 62 lt 1 204 4 ees a 116 Bll Questions for discussion ie s a eu pi p Pa pE A a e Q Q a 118 8 1 2 Phase Shift migration io aoaaa a 119 Bho Questions for disciesiom cr ssa e ec bae epe SE eS eke es 119 8 2 Lab Activity 10 FD FFD PSPI Split step Gaussian Beam v z z AON ona ee ee a Yu Sula ee ee Se eo de Qp a asa 119 8 3 Homework Assignment 4 Due 24 Sept 2015 Thursday session 28 Sept 2015 Tuesday group Migration comparisons 121 8 4 Concluding Remarks 24 6 a ta6 od eee Se ee Ge eee EE 121 Data before stack 122 9 1 Lab Activity 11 Reading and Viewing Seismic Data 122 9 1 1 Reading the data 4446648684 444645 6 peo a eee 123 9 2 Getting to know our data trace header values 123 9 21 Setting geometry 246 oom amp AS be ES 124 9 33 Getting to know our data Viewing the data 125 9 31 Waindowing Seismic Data RS 125 94 Getting to know your data Bad or missing shots traces or receivers 127 9 4 1 Viewing a specific Shot gather ___ _ a 127 9 4 2 Charting source and receiver positions 128 9 5 Geometrical spreading aka divergence correction 129 9 5 1 Some theory of sei
18. A Course in Geophysical Image Processing with Seismic Unix GPGN 461 561 Lab Fall 2015 Instructor John Stockwell Research Associate Center for Wave Phenomena copyright John W Stockwell Jr 2009 2015 all rights reserved License You may download this document for educational purposes and personal use only but not for republication November 2 2015 Contents 1 Seismic Processing Lab Preliminary issues 1 Motivation for the lab sasas ss k gos ote Re eh W ae ke a sls 1 2 Unix and Unix like operating systems o 1 2 1 Steep learning curve 2 a 2 s a se es awh Ld LGM s a s z s anis Sus 3 naaa Q SUK Sos S sU S aoa amp Sus baa l4 Whatisasbell stan s s ss Seb ede bee S a he Se eS U SW 1 5 The working environment _ _ a 02 ee eee 1 6 Setting the working environment _ _ 1 7 Choiee OF editor lt e s eke ne sn s na s k s a aq k eR ee W sn a 1 8 The Unix directory stirucfure _ a oe ee a es e ee 1 9 Scratch and Data directories ____ 200002 1 10 Shell environment variables and path 1 10 1 The path or PATH _ Ree wo Sa ew 1 10 2 The CWPROOT variable acca 5 29 oe b ooe 2 ok bee GEE 1 11 Shell configuration fles s posc we enn Ge ew A ew Se eee ak W 1 12 Setting up the working environment 2 The CSH family sesos ie ane e Be eS W Ga oe ee SE Cee N 1 12 2 The SH family lt c ec ea s ws Qo
19. T Entering Text Searching and Replacing a append after cursor w search forward for w A or a append at end of line w search backward for w i insert before cursor wl n search forward for wand move down n lines Tor _i insert at beginning of line n repeat search forward o open line below cursor N repeat search backward O open line above cursor cm change text m is movement s old new replace next occurence of old with new Cut Copy Paste Working w Buffers dm delete m is movement dd delete line Dord delete to end of line x delete char under cursor X delete char before cursor ym yank to buffer m is movement yy or Y yank to buffer current line p paste from buffer after cursor P paste from buffer before cursor bdd cut line into named buffer b a z bp paste from named buffer b s old new g replace all occurences on the line x ys old new g replace all ocurrences from line x to y s old newlg replace all occurrences in file s old new gc same as above with confirmation Miscellaneous n gt m indent n lines mis movement nam un indent left n lines mis movement repeat last command U undo changes on current line u undo last command J join end of line with next line at lt cr gt rf insert text from external file f G show status Figure 1 1 A quick reference for the vi editor I7 18 third party editors likely are sufficient for the purposes of this course For this class if you
20. a w sedat udp ta tit 1 13 Unix help mechanism Unix man pages _ o Lab Activity 1 Getting started with Unix and SU 2 1 Pipe redirect in lt redirect out gt and run in background amp 2 2 Stringing commands together aoaaa 84 r 2 2 1 Questions for discussion 26 ooo a a 2 3 Unix Quick Reference Cards a ex Lab Activity Z2 viewing data 3 0 1 Data image examples 2 4 22 422 dee Sele bee er e e eS 3 1 Viewing an SU data file Wiggle traces and Image plots Gell Wiggle TRACES qi g poe Se Bk kuu wwe Gow Sew W Gaisa eae ak x 3 12 Image plots so eee s ans k s Bo q h aQ be oS h uq 8 Q Bee amp 3 2 Greyscale sosi ata ee ee a WS S GE w Y ore me w 02 ee a E St ee s Q 3 3 Legend making grayscale values scientifically meaningful 3 4 Display balancing and display gaining 12 12 13 13 14 14 15 16 16 18 20 21 22 22 22 22 23 24 24 26 28 29 30 30 3 5 Homework problem 1 Due dates Thursday 3 Sept 2015 and Tuesday 8 September 2015 2 it s s s gs 3 de hak Se etee oe bed ea kay 3 6 Concluding Remarks 22243424 h264 64 ent oh eed s aq a dae a 3 6 1 What do the numbers mean a 84 ee eu Help features in Seismic Unix AT CThegsellfd6 4 4 4 0440 g e444 wa 6a q k w Q a e adits G al ee Q 4 2 Finding the names of programs with suname 4 3 Lab Activity 3 Exploring the trace header structure
21. al processing iva 11 2 1 The Forward and Inverse Fourier Transform 177 11 3 Convolution cross correlation and autocorrelation 178 11 3 1 Convolution aR Se S dk HO we See ES 178 11 3 2 Lab Activity 18 Frequency filtering 178 11 3 3 Lab Activity 19 Spectral whitening of the fake data 180 11 3 4 The Forward and Inverse Z transform 183 11 3 5 The inverse Z transform 1 be es 183 11A Deconvolution sos soe Q g Dane a Ae ke ee S G we ae ee e q U N 184 11 4 1 Convolution of a wavelet with a reflectivity series 184 11 4 2 Convolution with a wavelet 2 185 11 4 3 Deconvolution r a ae r we EES 186 11 4 4 Deconvolution of functions represented by their Z transforms 186 11 4 5 Division in the frequency domain Deterministic deconvolution 186 11 5 Cross and auto correlation 2 a a a r r es e e 189 11 5 1 Z transform view of cross correlation 189 11 5 2 Cross correlation and auto correlation in SU suxcor and suacor 191 11 6 Lab activity 20 Wiener least squares filtering 192 11 6 1 A matrix view of the convolution model 192 11 6 2 Designing wavelet shaping filters Wiener filtering 194 11 6 3 Least squares Wiener filter design 195 11 7 Spiking deconvolution o s es sors 2 w e w w a w w We 8 w ee Se lt N 196
22. are not already familiar with vi or some other editor I would recommend using gedit 1 8 The Unix directory structure As with other computing systems data and programs are contained in files and files are contained in folders In Unix and all Unix like environments folders are called directories The structure of directories in Unix is that of an upside down tree with its root at the top and its branches subdirectories and the files they contain extending downward The root directory is called pronounced slash While there exist graphical browsers on most Unix like operating systems it is more efficient for users working on the commandline of a terminal windows to use a few sim ple commands to view and navigate the contents of the directory structure Some of these commands are pwd print working directory Is list contents and cd change directory Locating yourself on the system If you type cd pwd 1s You will see your current working directory location which is your called your home directory You should see something like pwd home yourusername where yourusername is your username on the system Other users likely have their home directories in home or something similar depending on how your system administrator has set things up The command ls which is short for list will show you the contents of your home directory which may consi
23. aw a The dashed line is the interpreted reflector taken to be the envelope of the Cli 28 2 ead ee ok Rhee Se ee ee ee ea ee ee The light cone representation of the constant velocity solution of the 2D wave equation Every wavefront for both positive and negative time t is found by passing a plane parallel to the x z plane through the cone at the desired time t We may want to run time backwards for migration The light cone representation for negative times is now embedded in the x z t cube A seismic arrival to be migrated at the coordinates T is placed at the apex of the cone The circle that we draw on the seismogram for that point is the set of points obtained by the intersection of the cone with thet plane oe ew em mo kaq bok ore Swe k S ee ee ee Hagedoorn s method of graphical migration applied to the diffraction from a point scatterer Only a few of the Hagedoorn circles are drawn here but the reader should be aware that any Hagedoorn circle through a diffraction event will intersect the apex of the diffraction hyperbola The light cone for a point scatterer at z z By classical geometry a vertical slice through the cone in x t the z 0 plane where we record our data is a hyperbola Time migrations collapse diffraction hyperbolae to their respective apex points Depth migrations map these apex points tome r2 QD pline bi padre wa Pee ed ah k bee s G Cartoon showing the relationship between types of mi
24. ding on what the user is familiar with or is trying to accomplish Any of the above mentioned editors or similar 16 17 Vi Quick Reference http www sfu ca yzhang linux MOVEMENT lines ends at lt CR gt sentence ends at puncuation space section ends at lt EOF gt By Character Marking Position on Screen mp mark current position as p a z k p move to mark position p p move to first non whitespace on line w mark p h gt lt ee j By Line nG to line n 0 first last position on line or _ first non whitespace char on line first character on next prev line By Screen AF AB scroll foward back one full screen Miscellaneous Movement fm forward to character m Fm backward to character m tm forward to character before m Tm backward to character after m w move to next word stops at puncuation W move to next word skips punctuation b move to previous word stops at punctuation B move to previous word skips punctuation e end of word puncuation not part of word E end of word punctuation part of word AD AU scroll forward back half a screen next previous sentence AE Y show one more line at bottom top ll next previous section L go to the bottom of the screen next previous paragraph Z position line with cursor at top goto matching parenthesis Z position line with cursor at middle Z position line with cursor at EDITING TEX
25. e a broader understanding of the subject of seismic processing We seek also to help students develop some practical skills that will serve them in a general way even if they do not go into the field of oil and gas exploration and development Consequently we make use of freely available open source software the Seismic Unix package running on small scale hardware Linux based PCs Students are also encour aged to install the SU software on their own personal Linux or Mac PCs so that they may work and play with the data and with the codes at their leisure Given the limited scale of our available hardware and time our goal is modest to introduce students to seismic data processing through a 2D single component processing application The intended range of experience is approximately that which a seismic processor of mid to late 1970s might have experienced on a vastly slower more expensive and more difficult to use processing platform Our technology is different from that of the 1970s geophysicist This section is in cluded to help familiarize the student with that technology T2 13 1 2 Unix and Unix like operating systems The Unix operating system as well as any other Unix like operating system which includes the various forms of Linux UBUNTU Free BSD Unix and Mac OS X is commonly used in the exploration seismic community Consequently learning aspects of this operating system is time well spent Many users may have
26. e dates Thursday 3 Sept 2015 and Tuesday 8 September 2015 Repeat display gaining experiments of the previous section with radar su and seis mic su to see what median balancing and setting perc does to these data e Capture representative plots with axes properly labeled You can use the Linux screen capture feature or find another way to capture plots into a file such as by using supsimage to make PostScript plots Feel free to use different values of perc and different colormaps than were used in the previous examples Is median filtering better Is it worse Can you simply change the clip value and get a better picture The OpenOffice or LibreOffice Word wordprocessing program is an easy program to use for this e Prepare a report of your results The report should consist of Your plots you are telling a story show only images are relevant to your story a short paragraph describing what you saw Think of it as a figure caption a listing of the actual commandlines that you ran to get the plots Not more than 3 pages total Make sure that your name the due date and the assignment number are at the top of the first page e Save your report in the form of a PDF file and email to john dix mines edu 3 6 Concluding Remarks There are many ways of presenting data Two of the most important questions that a scientist can ask when seeing a plot are What is the meaning of the colorscale or gra
27. e prompt at the beginning of the commandline Do not type the when entering commands mkdir Tempi this creates the directory Temp1 cd Templ change working directory to Temp1 cp data cwpscratch Datal sonar su cp data cwpscratch Datal radar su cp data cwpscratch Datal seismic su AAA A This is a literal dot which means the current directory 1s should show the file sonar su For the rest of this document when you are directed to make Temp directories it will be assumed that you are putting these in your personal scratch directory 3 1 Viewing an SU data file Wiggle traces and Image plots Though we are assuming that the examples sonar su seismic su and radar su are finished products our mode of presentation of these datasets may change the way we view them entirely Proper presentation can enhance features we want to see suppress parts of the data that we are less interested in accentuate signal and suppress noise Improper presentation on the other hand can take turn the best images into something that is totally useless 3 1 1 Wiggle traces A common mode of presentation of seismic data is the wiggle trace Such a represen tation consists of representing the oscillations of the data as a graph of amplitude as a function of time with successive traces plotted side by side Amplitudes of one polarity usually positive are shaded black where as negative amplitudes are not shaded Be aware
28. e user either has a windowed user interface as the default or initiates such an interface with a command such as startx in some installations of Linux If you are unable to login on the laboratory machines you likely need to set your CSM MultiPass password For this you will need your Colorado School of Mines E Key which you obtained when you registered at the school 1 4 What is a Shell Some of the difficult and confusing aspects of Unix and Unix like operating systems are encountered at the very beginning of using the system The first of these is the notion of a shell Unix is an hierarchical operating system that runs a program called the kernel that is is the heart of the operating system Everything else consists of programs that are run by the kernel and which give the user access to the kernel and thus to the hardware of the machine The program that allows the user to interface with the computer is called the working shell The basic level of shell on all Unix systems is called sh the Bourne shell Under Linux based systems this shell is actually an open source rewritten version called bash the Bourne again shell but it has an alias that makes it appear to be the same as the sh that is found on all other Unix and Unix like systems The common working shell environment that a user is usually set up to login in under may be csh the C shell tesh the T shell which is a non proprietary version of csh ksh the Korn shell
29. ences in that the administrator may simply remove items that are too big or have a policy of removing items that have not been accessed over a certain period of time A system administra tor may also set up an automated grim file reaper to automatically delete materials that have not been accessed after a period of time Because files are not always automatically backed up and because hardware failures are possible on any system it is a good idea for the user to purchase USB storage media and get in the habit of making personal backups on a regular basis A less hostile mode of management is to institute quotas to prevent single users from hogging the available scratch space You may see a scratch directory on any of the machines in your lab but these are different directories each located on a different hard drive This can lead to confusion as a user may copy stuff into a scratch area on one day and then work on a different computer on a different day thinking that their stuff has been removed The availability and use of scratch directories is important because each user has a quota that limits the amount of space that he or she may use in his her home directory 20 21 On systems where a scratch directory is provided that also has write permission the user may create his her personal work area via cd scratch mkdir yourusername lt here yourusername is the your user name on the system Unless otherwise stated t
30. ency of the suplane test pattern via suspecfx UNIX Quick Reference card pl From the University References UNIX Quick Reference card p2 l 2 Image of sonar su data no perc Only the largest amplitudes are visible Image of sonar su data with perc 99 Clipping the top 1 percentile of amplitudes brings up the lower amplitude amplitudes of the plot Image of sonar su data with perc 99 and legend 1 Comparison of the default hsv0 hsv2 and hsv7 colormaps Rendering these plots in grayscales emphasizes the location of the bright spot in the color a 4 oe a a oe eee eae a we Ob Owe ale So eee Es Image of sonar su data with perc 99 and legend 1 Image of sonar su data with median balancing and perc 99 Comparison of seismic su median normalized with the same data with no median balancing Amplitudes are clipped to 3 0 in each case Notice that there are features visible on the plot without median balancing that cannot be seen on the median normalized data Cartoon showing the simple shifting of time to depth The spatial coor dinates z do not change in the transformation only the time scale t is stretched to the depth scale z Note that vertical relief looks greater in a depth section as compared with a time section a Test pattern b Test pattern corrected from time to depth c Test pattern corrected back from depth to time section Note that
31. gration a shows a point in 7 j b the impulse response of the migration operation in x z c shows a diffraction d the diffraction stack as the output point G2 gree a oe ey oe re te Bohs ooh ae ee ee 84 7 1 Te 7 3 7 4 7 5 7 6 9 1 9 2 9 3 9 4 9 5 9 6 9 7 a Spike data b the Stolt migration of these spikes The curves in b are impulse responses of the migration operator which is what the curves in the Hagadoorn method were approximating Not only do the curves repre sent every point in the medium where the impulses could have come from the amplitudes represent the strength of the signal from that respective location 4 woos k puls oe san S S oe Pee ee SUS See a The simple su data b The same data trace interpolated the interp su data You can recognize spatial aliasing in a by noticing that the peak of the waveform on a given trace does not line up with the main lobe of the neighboring traces The data in b are the same data as in a but with twice as many traces covering the same spatial range Each peak aligns with part of the main lobe of the waveform on the neighboring trace so there is no spatial aliasing lt o oa coou a Ge a Se we s Ee a Simple data in the f k domain b Interpolated simple data in the f amp domain c Simple data represented in the kz kz domain d In terpolated simple data in the k k domain The simple su data are truncated in the frequency domain
32. grown up with a point and click environment or a there is an app for that environment where a given program is run via a graphical user interface GUI featuring menus and assorted windows Certainly there are such software applications in the world of commercial seismic processing but none of these are inexpensive and none give the user access to the source code of the application There is also an expert user level of work where such GUI driven tools do not exist and programs are run from the commandline of a terminal window or are executed as part of a processing sequence in shell script In this course we will use the open source CWP SU Seismic Unix called simply Seis mic Unix or SU seismic processing and research environment This software collection was developed largely at the Colorado School of Mines CSM at the Center for Wave Phenomena CWP with contributions from users all around the world The SU soft ware package is designed to run under any Unix or Unix like operating system and is available as full source code Students are free to install Linux and SU on their PCs or use Unix like alternatives and thus have the software as well as the data provided for the course for home use during and beyond the time of the course The datasets are also open The major dataset that we will use in the course was put in the public domain by Mobil corporation in the early 1990s The student may have both the data and the
33. gt is a buffer which reads from standard input and writes to the file whose name is supplied to the right of the symbol Think of this as data pouring out of the program suplane into the file junk su The lest than sign lt is called redirect in and suxwigb lt junk su amp says run suxwigb reading the input from the file junk su run in background e pipe from program to program 28 29 a trace number b trace number 10 20 30 10 20 30 0 05 0 104 604 time s lt e lt Freq Hz k 0 154 bry dy 0 204 1004 1205 0 254 suplane test pattern Figure 2 2 a The suplane test pattern b the Fourier transform time to frequency of the suplane test pattern via suspecfx e gt write data from program to file redirect out e lt read data from file to program redirect in amp run program in background 2 2 Stringing commands together We may string together programs via pipes and input and output via redirects gt and lt An example is to use the program suspecfx to look at the amplitude spectrum of the traces in data made with suplane suplane suspecfx suxwigb amp make suplane data find the amplitude spectrum plot as wigg
34. his text will assume that you are conducting further operations in your personal scratch work area For our system the scratch directory that we will work in is gpfc so your instructions are to cd gpfc mkdir yourusername lt here yourusername is the your user name on the system The directory gpfcyourusername will be your preferred scratch or working area 1 10 Shell environment variables and path The working shell is a program that has a configuration that gives the user access to executable files on the system Recall that echoing the value of the SHELL variable echo SHELL lt returns the value of the users working shell environment tells you what shell program is your working shell environment There are other envi ronmental variables other than SHELL Again note that if this command returns one of the values bin sh bin ksh bin bash bin zsh then you are working in the SH family and need to follow instructions for working with that type of environment If on the other hand the echo SHELL command returns one of the values bin csh bin tcsh then you are working in the CSH family and need to follow the alternate series of in structions given In the modern world of Linux it is quite common for the default shell to be something called binbash an open source version of binsh 21 22 1 10 1 The path or PATH Another important variable is the path or PATH The value path variab
35. inistrator Each computer in this lab has a directory called scratch that is provided as a temporary workspace for users It is in this location that you will be working with data Create your own scratch directory via mkdir gpfc yourusername Here yourusername is the actual username that you are designated as on this system Please feel free to ask for help as you need it The gpfc directory may reside physically on the computer where you are sitting or it may be remotely mounted In computer environements where the directory is locally on the a given computer you will have to keep working on the same system If you change computers you will have to transfer the items from your personal scratch area to that new machine In labs where the directory is remotely mounted you may work on any machine that has the directory mounted Remember scratch directories are not backed up If you want to save materials permanently it is a good idea to make use of a USB storage device 3 0 1 Data image examples gt 06 Three small datasets are provided These are labeled sonar su radar su and seis 7 a mic su and are located in the directory data cwpscratch Datat We will pretend that these data examples are data images which is to say these are examples that require no further processing Do the following cd gpfc yourusername this takes you to gpfc yourusername 33 34 This represents th
36. le no median amp compared with applying the median balancing sunormalize norm balmed lt seismic su suximage wbox 250 hbox 600 cmap hsv4 clip 3 title median filtering amp This result looks bizarre because the traces individually have different median values and consequently have different ranges of amplitudes An improved picture may be obtained by applying an RMS normalization to the traces after they have been median filtered via sunormalize norm balmed lt seismic su sunormalize norm rms suximage wbox 250 hbox 600 cmap hsv4 clip 3 title median filtering amp In each of these examples the line is broken to fit on the page When you type this the pipe follows immediately after the seismic su There are other possibilities We may consider simply normalizing the data by the maximum or minimum value or by some other constant Furthermore we have the question of whether the process be applied trace by trace or over the whole panel of data 42 43 400 200 LO O 0 d perc 99 ing an Image of sonar su data with median balanci Figure 3 6 43 44 68357 9 0 30397 999 9 Figure 3 7 Comparison of seismic su median normalized with the same data with no median balancing Amplitudes are clipped to 3 0 in each case Notice that there are features visible on the plot without median balancing that cannot be seen on the median normalized data 44 45 3 5 Homework problem Z1 Du
37. le tells the location that the working shell looks for executable files in Usually executables are stored in a sub directory bin of some directory Because there may be many software packages installed on a system there may be many such locations To find out what paths you can access which is to say which executables your shell can see type echo path or echo PATH 66 99 The result will be a listing separated by colons of paths or by spaces to executable programs 1 10 2 The CWPROOT variable The variable PATH is important but SHELL and PATH are not the only possible envi ronment variable Often programmers will use an environment variable to give a users shell access to some attribute or information regarding a specific piece of software This is done because sometimes software packages are of restricted interest For SU the path CWPROOT is necessary for running the SU suite of programs We need to set this environment variable and to put the suite of Seismic Unix programs on the users path 1 11 Shell configuration files Because the users shell has as an attribute a natural programming language many configurations of the shell environment are possible To find the configuration files for your operating system type ls a lt show directory listing of all files and sub directories pwd lt print working directory then the user will see a number of files whose names begin
38. le traces Equivalently we may do suplane gt junk su make suplane data write to a file suspecfx lt junk su gt junk1 su find the amplitude spectrum write to a file suxwigb lt junki su amp view the output as wiggle traces This does exactly the same thing in terms of final output as the previous example with the exception that here two files have been created See Figure 2 2 29 30 2 2 1 Questions for discussion e What is the Fourier transform of a function e What is an amplitude spectrum e Why do the plots of the amplitude spectrum in Figure 2 2 appear as they do 2 3 Unix Quick Reference Cards The two figures Fig 2 3 and Fig 2 4 are a Quick Reference cards for some Unix commands References Sobell M 2010 A practical guide to Linux commands editors and shell program ming Pearson Education Inc Boston MA 30 31 I0q sqnds Jm np pupnipur wway din 0 I SAO 1q INOA JOS GIA PIM PHOM y UO SPINS sry ssadoe o 9661 Isn ny BI sue jeuondo Ou JO Sak qELIPA pou 1 mduuoo Joquinu uupu uJ Ju uuuolIAu AOJOIIP x ssaid pue Ady ouo umop POY X49 1 uduued siy u p sn suoneinasqqy pied IDUJ spuewwo xtun S3J3JIANXNAS ADOIONHOAL NOILVWYOANE ALISYAAINA 8086 LL04 SOLOJOALIP WAS S JOU 194 980 POYUT Ge s rtO 1Ip Si9sn A UO WOU UO pal eysUL aeos oy N A UO upo NOA WOI OUI pagg AL NOK JI I9A AOH LSI VIIA
39. mic data may be thought of as an array of floating point numerical values each representing a seismic amplitude at a specific t x location A plot consisting of an array of gray or color dots with each gray level or color representing the respective value is called an image plot If we view An alternative is an image plot suximage lt sonar su amp This should look better We usually use image plots for datasets of more than 50 traces We use wiggle traces for smaller datasets 3 2 Greyscale There are only 256 shades of gray available in this plot If a single point in the dataset makes a large spike then it is possible that most of the 256 shades are used up by that one amplitude Therefore scaling amplitudes is often necessary The simplest processing of the data is to amplitude truncate clip the data The term clip refers to old time strip chart records which when amplitudes were too large appeared if someone had taken scissors and clipped of the tops of the sinusoids of the oscillations Try suximage lt sonar su perc 99 amp suximage lt sonar su perc 99 legend 1 The perc 99 passes only those items of the 99th percentile and below in amplitude You may need to look up percentile on the Internet In other words it clips amplitude truncates the data to remove the top 1 per cent of amplitudes Try different values of perc to see what this does 35 36 200 400 0 05
40. n Lab Activity 17 Radon transform 157 10 2 1 Homework assignment 6 Due Thursday 8 Oct 2015 before 9 00am and on Tues 13 Oct 2015 2 2 ae ae eee wa ee Ee BR 160 10 2 2 We are not finished with multiple suppression and velocity analysis 162 10 3 Mutine revisited o sece s kiana eed be Xe hee ERG Sd Ee 162 10 3 1 The stretch mute 2 0 6 26 G ere ec Bee ea Gee ee EO 162 10 3 2 Muting specific arrivals 2 4 24 be ee ee ae es 164 10 3 3 Lab Activity 16 muting the data 165 10 3 4 Identifying waves to be muted 0 2 000 165 10 3 5 How to pick mute values 2 0 a a 165 10 3 6 The shape of the wavelet 2 a a a a ee 166 10 3 7 Further processing 0 4 4 24 6 eee oa hee 6 oe Oak s s 167 10 3 8 The at command using the computer while you are asleep 168 10 4 Homework Assignment 7 due Thursday 15 Oct 2015 and Tuesday 27 October 2015 before 9 00 AM ooa 44 we wea oa Boe ee ES 170 10 5 Concluding remarks 4 0 64 26 eho dee we ew oo ae eee ee 172 11 Spectral methods and advanced gaining methods for seismic data 173 11 1 Common assumptions of spectral method processing 173 11 11 Causality lt uma Wo eS p a OR ar he eWeek OH 175 11 1 2 Minimum phase aka minimum delay 175 11 1 3 Whitespectruni lt Q s sedans oe S 4 ke ee EE wee qD B 175 L114 Linear systems 2 2444 g usss ws hee ach bad entere 176 11 2 The three mathematical languages of sign
41. ng on Unix like systems a lot then taking the time to learn vi is also time well spent The vi editor is the only editor that is guaranteed to be on all Unix like systems All other editors are third party items that may have to be added on some systems sometimes with difficulty Similarly there is an editor called emacs that is popular among many users largely because it is possible to write programs in the LISP language and implement these within the emacs environment There is also a steep learning curve for this language There is often substantial configuration required to get emacs working in the way the user desires A third editor is called pico which comes with a mailer called pine Pico is easy to learn to use fully menued and runs in a terminal window The fourth class of editor consists of the screen editors Popular screen editors include xedit nedit and gedit There is a windowed interfaced version of emacs called xemacs that is similar to the first two editors These are all easy to learn and to use Not all editors are the best to use The user may find that invisible characters are introduced by some editors and that there may be issues regarding how wrapped lines are handled that may cause problems for some applications These issues are another incentive for an expert user such as a Unix system administrator to prefer vi over other more intuitive editors The choice of editor is often a highly personal one depen
42. nn4d auy o f opf nding u0ndui2s 3 1 wed auwipu umu Weu uA yq auipULasn EUI UOISS S ux HJ dus f daquiad q d pugwuop di H 32 uoneoSiunuutuo2 Indiano U pupunuoo JU2924 PUGN uj spuupunuoo Ju 2 4 Kojds q Kosy AMLOJIAAIP BUIYAOM Ulf pmd uoupunofur sauf ASUDYD ujyo UOIDUAOfUL sasn mdmo awpusasn utuj 4asn Juasano KD dsiC ILIBOUA S4 SN U1 Passo IST oym IUN 22 ADP Uld Iep monb ys p amp ojds q gwonb S n pA JUGUUOAIAUA JUL faupu Au juud saspyp pupunuoo kpydsiq aupu sene rolap ut sajf 1817 fl Si COLasIp ut SAUL INT FI Pl si uondtr s q pueunuo9 Sn1e1S 1u uuuoulAuj 2 qD14DA JUPUUOLIAUA PAOWA A AN DA 01 ADA Aua Jas UOISSaS JDUIULAAL PUY pOu aJOWAd 01 W180 PUDU SPID PUDULUOD aAOWlay SDD PUDUIUOD IDAJ p4omsspd asupyy Zp sp p Kaopasip aumuay p Golo p ol f apf AOW p amp sopasip aaoulay P Golo 4Ip Mau IWA p Golo 4tp ol asuDYyD uo0ndui S I z umu jawou Auajesun A ltDu NUJ mogo pu utoj jatupu seieun umu I tupu SELE pmssed ZP Ip su piv if su p upu P zpw P po puguuuoo Ionuoo 1u uuuouiAaug UNIX Quick Reference card p2 32 Figure 2 4 Chapter 3 Lab Activity 2 viewing data Just as scratch paper is paper that you use temporarily without the plan of saving for the long term a scratch directory is temporary working space which is not backed up and which may be arbitrarily cleared by the system adm
43. o his her home don t type the dollar sign directory In these notes the symbol will represent the commandline prompt The user does not type this Because there are a large variety of possible prompt characters or strings of characters that people use for the propmt we show here only the dollar sign as a generic commmandline prompt On your system it might be a a gt or some combination of these with the computer name and or the working directory and or the commandline number echo SHELL lt returns the value of the users working shell environment type this dollar sign The command echo SHELL tells your working shell to return the value that denotes your working shell environment In English this command might be translated as print the value of the variable SHELL In this context the dollar sign in front of SHELL should be translated as value of Thus echo value of SHELL Common possible shells are bin sh lt the Bourne Shell bin bash lt the Bourne again Shell bin ksh lt K shell bin zsh lt Z shell bin csh lt C shell bin tcsh lt T shell The environments sh bash ksh and zsh are similar We will call these the sh family The environments csh and tcsh are similar to each other but have many differences from the sh family We refer to csh and tcsh as the csh family Again on Linux and Mac OX systems bin bash is usually the default working shell
44. smic amplitudes 129 9 5 2 Lab Activity 12 Gaining the data 26 2 454 i044 x 130 9 5 3 Statisticalgaining 4544 pees Redes eee ee ee s 131 9 5 4 Model based divergence correction _ a a a a a 133 9 6 Getting to know our data Different Sorting Geometries 133 9 6 1 Lab Activity 13 Common offset sgathers __ __ 133 9 6 2 Lab Activity 14 CMP CDP Gathers 134 9 6 3 BOP and Pai ke ao mos n sam Be eee BOS ew ole B ch G 134 9 64 Viewing the headers _ _ a 136 96 5 Stacking Chart s lt suls g ab bee qua puyuk Ch bee 6 SU be EH 139 9 6 6 Capturing a Single CMP gather be 139 9 7 Quality control through raw CV and brute stacks 142 9 7 1 Lab Activity 15 Raw Stacks CV Stacks and Brute Stacks 142 9 8 Homework 5 Due Thursday 1 Oct 2015 and Tues 6 Oct 2015 prior to 9 00AM saei sas s be She ork oe Oe y ee BES hoe ew a a 143 9 8 1 Are we done with gaining 004 144 9 g Concluding Remarks 06 44444 64 4496 aee wee Hee e He 144 10 Velocity Analysis Preview of Semblance and noise suppression 146 10 0 1 Creative use of NMO and Inverse NMO 149 10 1 The Radon or r p Transform lt lt o 0 0 ends ie od Be Se SoS 149 10 1 1 How filtering in the Radon domain differs from f k filtering 152 10 1 2 Semblance and Radon fora CDP gather 152 10 2 Multiple suppressio
45. software for his her own continuing education after the course is finished 1 2 1 Steep learning curve The disadvantage that most beginning Unix users face is a steep learning curve owing to the myriad commands that comprise Unix and other Unix like operating systems The advantages of software portability and flexibility of applications as well as superior networking capability however makes Unix more attractive to industry than Microsoft based systems for these expert level applications While a user in an industrial envi ronment may have a Microsoft based PC on his or her desk the more computationally intensive processing work is done on a Unix based system The largest of these are clus ters composed of multi core multiprocessor PC systems It is not uncommon these days for such systems to have several thousand cores which is to say subprocessors Thus massive parallelism is available in the industry environment Because a course in seismic processing is of broad interest and may draw students with varied backgrounds and varied familiarity with computing systems we begin with the basics The reader familiar with these topics may skip to the next chapter 13 14 1 3 Logging in As with most computer systems there is a prompt usually containing the word login or the word username that indicates the place where the user types his or her login name The user is then prompted for a password Once on the system th
46. st of files or other subdirectories The codes for Seismic Unix are installed in some system directory path We will assume that all of the CWP SU Seismic Unix codes are located in usr local cwp 18 19 This denotes a directory cwp which is the sub directory of a directory called local which is in turn is a subdirectory of the directory usr that itself is a sub directory of slash It is worthwile for the user to spend some time learning the layout of his or her directories There is a command called df which shows the hardware devices that constitute the available storage on the users machine A typical output from typing df df h Filesystem Size Used Avail Use Mounted on dev sdal 286G 19G 253G 7 none 4 0K O 4 0K 0 sys fs cgroup udev 3 9G 4 0K 3 9G 1 dev tmpfs 795M 1 1M 794M 1 run none 5 0M O 5 0M 0 run lock none 3 9G 488K 3 9G 1 run shm none 100M 44K 100M 1 run user fermat u 2 0T 1 3T 664G 66 u fermat gpfc 3 0T 1 1T 1 81 38 gpfc isengard class 15G 562M 14G 4 class isengard usr local cwp 20G 17G 2 2G 89 usr local cwp isengard scratch 378G 270G 90G 76 scratch isengard data 99G 52G 42G 56 data isengard data cwpscratch 30G 6 9G 22G 25 data cwpscratch Note items in the far left column Those whose names that begin with dev are hardware devices on the specific computer The items that begin with a machine name in this case isengard mines edu
47. terpretable by a poor selection of colormapping This effect may be seen in Figure 3 4 Repeat the previous this time clipping by percentile suximage lt sonar su legend 1 perc 99 amp The ease at which colorscales are defined and the fact that there are no real standards on colorscales mean that effectively every color plot you encounter requires a colorscale for you to be able to know what the values mean Furthermore some colors ranges are brighter than others By moving the bright color to a different part of the amplitude range you can totally change the image This is a source of richness of display but it is also a potential source of trouble if the proper balance of color is not chosen 3 4 Display balancing and display gaining A common data amplitude balancing is to balance the colorscale on the median values in the data The median is the middle value meaning that half the values are larger than the median value and half the data are less than the median value Thus the traces are normalized by this middle value Another possibility is to scale traces by dividing by some constant value For example dividing each trace by the square root of the average of the sum of the square of its values RMS Type these commands to see that in SU sunormalize norm balmed lt sonar su suximage legend 1 sunormalize norm balmed lt sonar su suximage legend 1 perc 99 38 200 400 0 05 0 10 Figure 3 3 Image of
48. that such presentation introduces a bias in the way we view the data accentuating the positive amplitudes Furthermore wiggle traces may make dipping structures appear fatter than they actually are owing to the fact that a trace is a vertical slice through the data In SU we may view a wiggle trace display of data via the program suxwigb For example viewing the sonar su data as wiggle traces is done by redirecting in the data file into suxwigb suxwigb lt sonar su amp 34 35 the ampersand amp means run in background so you get your commandline back This should look horrible The problem is that there are 584 wiggle traces side by side Place the cursor on the plot and drag while holding down the index finger mouse button This is called a rubberband box Try grabbing a strip of the data of width less than 100 traces by placing the cursor at the top line of the plot and holding the index finger mouse button while dragging to the lower right Zooming in this fashion will show wiggles The less on here is that you need a relatively low density of data on your print medium for wiggle traces Place the mouse cursor on the plot and type q to kill the window Try the seismic su and the radar su data as wiggle traces via suxwigb lt seismic su amp suxwigb lt radar su amp In each case zoom in on the data until you are able to see the oscillations of the data 3 1 2 Image plots The seis
49. the curvature seen depth section indicates a non piecewise constant u t Note that the reconstructed time section has waveforms that are distorted by repeated sinc interpolation The sinc interpolation applied in the depth to time calculation has not had an anti alias filter applied 2 2 36 37 39 40 Al 43 44 67 5 3 6 1 6 2 6 3 6 4 6 5 6 6 OT 6 8 6 9 6 10 a Cartoon showing an idealized well log b Plot of a real well log A real well log is not well represented by piecewise constant layers c The third plot is a linearly interpolated velocity profile following the example in the text This approximation is a better first order approximation of a real well log 2242 6844268268 be eee 2s bo wos ae bY Geometry of Karcher s prospect note semicircular arcs indicating that Karcher understood the relation of surfaces of constant traveltime to what is seen on SeisMograM s s sos owe ook oe 6 w Ew won w w eS a Synthetic Zero offset data b Simple earth model The Hagedoorn method applied to the arrivals on a single seismic trace Hagedoorn s method applied to the simple data of Fig 6 2 Here circles each centered at time t 0 on a specific trace pass through the maximum amplitudes on each arrival on each trace The circle represents the locus of possible reflection points in z z where the signal in time could have originated ga sa eee seek ba ee eh Se Pts ae eee c
50. usr local cwp and echo PATH will yield lib u yourusername bin usr bin X11 usr local bin bin usr bin usr local bin usr sbin usr local cwp bin 23 24 1 12 2 The SH family The process is similar for the SH family of shells The file of interest has a name of the form profile bashre and the bash_profile The bash_profile is read once by the shell but the bashrc file is read everytime a window is opened or a shell is invoked Or vice versa depending on the system Mac OS X seems to have a strange convention Thus what is set here influences the users complete environment The default form of this file may show a path line similar to PATH PATH HOME bin usr local bin which should be edited to read export CWPROOT usr local cwp PATH PATH HOME bin usr local bin CWPROOT bin The important part of the path is to add the CWPROOT bin on the end of the PATH line no matter what it says The user then logs out and logs back in for the changes to take effect In each case the PATH and CWPROOT variables are necessary to be set for the users working shell environment to find the executables of Seismic Unix 1 13 Unix help mechanism Unix man pages Every program on a Unix or Unix like system has a system manual page called a man page that gives a terse description of its usage For example type man ls man cd man df man sh man bash man csh
51. which is proprietary zsh which is an open source version of Korn shell or bash which is an open source version of the Bourne shell On Linux and Mac OS X systems bash is the default shell environment The user has access to an application called terminal in the graphical user environ ment that when launched usually by double clicking on an icon that looks like a small video monitor invokes a window called a terminal window The word terminal harks back to an earlier day when a physical device called a terminal a screen and keyboard but no mouse constituted the users interface to the computer It is at the prompt on the terminal window that the user has access to a commandline where Unix commands are typed Most commands on Unix like systems are not built in commands in the shell but are actually programs that are run under the users working shell environment The shell commandline prompt is asking the user to input the name of an executable program That program may be a system command such as a directory folder listing or it may be a program written by a third party or by the user him herself 14 15 1 5 The working environment In the Unix world all filenames program names shells and directory names as well as passwords are case sensitive in their input so please be careful in running the examples that follow If the user types cd lt change directory with no argument 2 takes the user t
52. with a dot 1 12 Setting up the working environment One of the most difficult and confusing aspects of working on Unix like systems is en countered right at the beginning This is the problem of setting up user s personal environment There are two sets of instructions given here One for the CSH family of shells and the other for the SH family 22 23 1 12 1 The CSH family Each of the shell types returned by SHELL has a different configuration file For the csh family tcsh csh the configuration files are cshre and login To configure the shell edit the file cshrc Also the path variable is lower case You will likely find a line beginning with set path with entries something like set path lib bin usr bin X11 usr local bin bin usr bin usr local bin usr sbin Suppose that the Seismic Unix package is installed in the directory usr local cwp on your system Then we would add one line above to set the CWPROOT environment variable And one line below to define the user s path setenv CWPROOT usr local cwp set path lib bin usr bin X11 usr local bin bin usr bin usr local bin usr sbin set path path CWPROOT bin Save the file and log out and log back in You will need to log out completely from the system not just from particular terminal windows When you log back in and pull up a terminal window typing echo CWPROOT will yield
53. with the aliased portions folded over to lower wavenumbers The interpolated data are not folded a simple su data unfiltered b simple su data filtered with a 5 10 20 25 Hz trapezoidal filter c Stolt migration of unfiltered data d Stolt migra tion of filtered data e interpolated data f Stolt migration of interpolated data Clearly the most satisfying result is obtained by migrating the in terpolated data sa oa betwee eit 2 Owe Che eee ee ee eee Ee The results of a suit of Stolt migrations with different dip filters applied The k1 k2 domain plots of the simple su data with the respective dip filters applied in the Stolt migrations of Figure 7 5 The first 1000 traces in the data 0 000000 eee a Shot 200 as wiggle traces b as an image plot Gaining tests a no gain applied b tpow 1 c tpow 2 d jon 1 Note that in the text we often use jon 1 because it is convenient not because it is optimal It is up to you to find better values of the gaining parameters Once you have found those you should continue using those Common Offset Sections a offset 262 meters b offset 1012 meters c offset 3237 meters Gaining is done via sugain jon 1 A stacking chart is merely a plot of the header CDP field versus the offset field Note white stripes indicating missing shots CMP 200 f the gained data lt oc kd a a e sq koa w ee ee eS Se eK a Raw stack
54. y levels of nested directories to navigate 1 9 Scratch and Data directories Directories with names such as scratch and data are often provided with user write permission so that users may keep temporary files and data files out of their home direc tories Like scratch paper a scratch directory is usually for temporary file storage and is NOT BACKED UP Indeed on any computer system there may be other unbacked up directories You need to be aware of which parts of your computer system are backed up and which are not Because there are no backups on scratch directories it is important for the user to purchase a USB device to back up his or her items from the scratch areas Some directories may be physically located on the specific machine were you are seated and may not be visible on other machines Because the redundancy of backups require extra storage most system administrators restrict the amount of backed up space to a relatively small area of a computer system To restrict user access quotas may be imposed that will prevent users from using so much space that a single user could fill up a disk However in scratch areas there usually are no such restrictions so it is preferable to work in these directories and save only really important materials in your home directory Users should be aware that administration of scratch directories may not be user friendly Using up all of the space on a partition may have dire consequ
55. you should see the same output by typing suplane gt junk su suxwigb lt junk su title suplane test pattern labeli time s label2 trace number amp Finally we often need to have graphical output that can be imported into documents In SU we have graphics programs that write output in the PostScript language supswigb lt junk su title suplane test pattern labell time s label2 trace number gt suplane eps 2 1 Pipe redirect in lt redirect out gt and run in background amp In the commands in the last section we used three symbols that allow files and programs to send data to each other and to send data between programs The vertical bar is called a pipe on all Unix like systems Output sent to standard out may be piped from one program to another program as was done in the example of suplane suxwigb amp which in English may be translated as run suplane pipe output to the program suxwigb where the amp says run all commands on this line in background The pipe is a memory buffer with a read from standard input for an input and a write to standard output for an output You can think of this as a kind of plumbing A stream of data much like a stream of water is flowing from the program suplane to the program suxwigb The greater than sign gt is called redirect out and suplane gt junk su says run suplane writing output to the file junk su The
56. yscale of a plot and What normalization or balancing has been applied to the data before the plot The answers to these questions may be as important as the answer to the question What processing has been applied to these data 3 6 1 What do the numbers mean The scale divisions seen on the plots in this chapter that have been obtained by running suximage with legend 1 show numerical values values that are changed when we apply display gain Ultimately these numbers relate to the voltage recorded from a transducer a geophone hydrophone or accelerometer While in theory we should be able to extract information about the size of the ground displacement in say micrometers 45 46 or the pressure field strength in say megapascals there is little reason to do this Owing to detector and source coupling issues and the fact that data must be gathered quickly we really are only interested in relative values References Stockwell Jr J W and J K Cohen 2008 The new SU users manual available from http cwp mines edu cwpcodes 46
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