AMatlabGUIforusewithISOLAFortrancodes

UsersGuide

byEfthimiosSokos1)andJiriZahradnik2)

1) UniversityofPatras,SeismologicalLaboratory

2) CharlesUniversityinPrague,FacultyofMathematicsandPhysics

esokos@upatras.gr,jz@karel.troja.mff.cuni.cz

Ver.4.0

February2009

Contents

Whatisnewinver.4.0?........................................................3

GUIPurpose...........................................................................4

Requirements.........................................................................4

Installation.............................................................................5

Method..................................................................................5

RunningtheGUI...................................................................11

CrustalModel.................................................................................12

EventInfo.......................................................................................13

StationSelection.............................................................................14

RawDataPreparation.....................................................................15

TrialSourceDefinition....................................................................18

GreenFunctionComputation..........................................................21

Inversion.........................................................................................22

Plotting...........................................................................................25

UtilitiesIandII...............................................................................32

Acknowledgments................................................................34

AppendixIHowtoprepareapoleandzerofileforISOLA...35

AppendixII:Filesandfolders................................................38

Whatisnewinver.4.0?Thenew versionof ISOLAGUIhas somemajor changes/additions thatmaketheuseofthesoftwarealoteasier.Thefollowingarenew:

Theinstallationprocessisdifferent,ISOLAGUIrunsfromacertainfolderand ISOLA*.exefileshavetobeadded inthesystempathwhileISOLAGUIfileshavetobeaddedinMatlabpath

ISOLAGUI isperforminga checkwhen it is called fromwithinafolder and creates the folder structure or copies required filesautomatically ifneeded (e.g.whenwe startprocessingofaneweventandfiles,foldersdontexist)

Fileswithstationcoordinates,crustalmodelorpolesandzeroescan be stored in the installation folder and ISOLAGUIwill copythemtospecificrunfolder,automatically

A toolhasbeenadded,theautosacfile importgui,whichtriestoautomate the SAC file conversion to ISOLA format, user selectsonlyonefile,theNScomponentandtheGUIfindsand loadstheothertwo

Two more file format filters were added PITSA and SEISAN(pitsaimport.m,seisanimport.m)

Timesearch limitshavebeenextended,theusercanselectupto2500timeshiftsduringtheinversionprocedure

A new plot of DC versus correlation has been added (seeZahradniketal2007).

ToolstoconvertplotsinPNGformathavebeenadded. MTsol.txt file has a slightly different format to make it more

descriptiveandaccurate. Anewfilewithonelinesolution,reportwasadded. Trial source positions are saved in KML format for display in

GoogleEarth. AnewGUItohelpwithpolezerofilepreparationhasbeenadded. Various bugs have been corrected, and a few news were

added.!!!pleasesendusyourfeedback plusmanymoresmallchanges..!

Overallweconsiderthisamajorupdateandurgeuserstoupdate.

GUIPurpose

TheISOLAGUIhasbeencreatedusingtheMatlabGUIDEtool.Itspurposeistohelp

the user of ISOLAFORTRAN part with data preprocessing, Green function

preparation,waveform inversionanddisplayoftheresults. Inadditiontothemain

toolsafewutilitiesarealsopresentthathelptheuserto inspectthequalityofthe

datausingfilters,converttodisplacement,etc. Inutilitiestherearealsotwoother

options that could help: Backup files and Create Pole Zero file. The Backup files

optionsaves inauserspecifiedfolderanumberoffilesthatarecriticalforrunning

the inversion; in thisway the user can keep track of various attempts during an

experiment. Finally the import SAC andGCF (GuralpCompressed Format)options

help convertingSACandGCFbinary files in ISOLAascii format (4 columnsofascii

dataperstation,i.e.,Time,NS,EWandZcomponent).

Requirements

InordertouseISOLAGUI,youneedtohavethefollowingsoftwareinstalled

Matlab6.5or7.0(thesoftwarehasnotbeentestedusingotherversionsofMatlab)

GenericMappingTools (GMT,WesselandSmith,1991,1998) (thesoftwarewastestedusingversion4.0and4.1,newerversionsshouldworkalso)

M_Map,this isafreewareMatlabbasedpackage, it isused inmapcreationwithin Matlab, you can download

fromhttp://www2.ocgy.ubc.ca/~rich/map.htmlandyouhavetoadditin

theMatlabpath.

Ghostscript and GsView for Postscript filesdisplayhttp://www.cs.wisc.edu/~ghost/,youhavetoadditinthesystem

path.

ImagemagickconvertsPostscriptfilesinPNGformatfordisplayinwebpages,thisshouldbeinthesystempathtoo.

Installation

ISOLAandISOLAGUI,installationiseasyandneedsjustthreesteps

Step1:Unzip the zippeddistribution file ina folder likee.g.c:\matlab. Makesure thatyouhave selected theUse foldernamesoption (ifyouuseWinZip)ora

similaroptioninyourunzipsoftwarethatwillkeepthefoldernamesthatarestored

in the archive. After extracting you should have a main folder e.g.

c:\matlab\isola,which is your ISOLAGUI installation folder, and containsvariousMatlabfilesplusthreefolders,\bin,\pzfiles,\fortran.

Step2:AddtheinstallationfolderinMatlabpath(e.g.withinMatlabgotoFile,Set

Path,Addfolderandselecttheinstallationfolder,thenpressSaveandClose).

Step 3: Folder \isola\binholds theexecutablese.g.gr_xyz.exe, isola.exeetc, this folder has to be added in System path (go to Control Panel, System,

Advanced, Environment variable and add the \isola\bin folder in the Path under

Systemvariables).ISOLAGUIisnowinstalled.

Testingtheinstallation

FromwithinMatlabcommandwindowtypeisolaandpressenter,theISOLAGUIshouldstartinitializinginthecurrentfolder,ifnotchecktheabovesteps.

Method

ISOLA isbasedonmultiplepointsourcerepresentationand iterativedeconvolution

method,similartoKikuchiandKanamori(1991)forteleseismicrecords,butherethe

fullwavefield is considered, andGreen's functions are calculated by the discrete

wavenumbermethodofBouchon(1981).Thusthemethodisapplicableforregional

and local events. Instrumentally corrected bandpass filtered velocity records are

used.Thecodetransformsvelocityintodisplacement,invertsthedisplacement,and

providessyntheticdisplacement.Seismograms(t)isapproximatedbyacombination

ofelementaryseismogramsei(t), i=1,2,...6, i.e.s(t)=sum(ai .ei(t)).Theelementary

seismogramscorrespondtobasicfocalmechanismsasfollows:

istrikediprake

10900

22709090

309090

4904590

504590

6isotropic

Seismograms(3component),fromasetofstations,representthedata,d,whilethe

coefficientsaiaretheparameterstobefound,m.Thelinearinverseproblemd=Gm

issolvedbytheleastsquaremethod:m=(GTG)1GTd,whereGTisGtransposed

and ()1 is the inverse of the socalled systemmatrix (GT G). Eigenvalues of the

systemmatrix(GTG)arecalculatedtounderstandhowwellposed(orillposed)the

inverseproblem is.Ratioofmin/maxeigenvalue is reported.The lower thevalue,

theworsetheresultsare(although,formally,thequalityofthefitmaybegood,e.g.

variancereductioncanbelarge).Questionhowtheindividualstationscontributeto

thewellposedinversionhasnosimpleanswer.Itistobecarefullyanalyzedcaseby

case.

Optionally, theweighted inversion isperformed,withweightsprescribedbyuser,

differentweights for different stations and components. As a rule, upweighting

records with small amplitudes, and downweighting large amplitudes, is

recommended.Anotherstrategyistoupweightstationswhoseseismogramsappear

tobethemostsensitivewithrespecttosmallmodificationsoftheproblem.

ThecoefficientsaiarerelatedtomomenttensorMpq(wherep,qrefertogeographic

coordinatesx(>0,N),y(>0,E),z(>0,up)):

Mxx=a4+a6

Myy=a5+a6

Mzz=a4+a5+a6

Mxy=Myx=a1

Mxz=Mzx=a2

Myz=Mzy=a3

Moment tensor components in spherical coordinates r, t(=theta), p(=phi), used in

Harvardcatalogue,orinGMT,aregivenby:

Mtt=Mxx

Mpp=Myy

Mrr=Mzz

Mtp=Mxy

Mrt=Mxz

Mrp=Myz

Eigenvectorsofthemomenttensorprovidestrike,dipandrake.Eigenvaluesprovide

scalar moment Mo and decomposition of the moment tensor into three parts:

doublecouple(DC),compensatedlinearvectordipole(CLVD),andvoluminial(VOL).

Possiblemomenttensor(MT)inversionmodesareasfollows:

fullMTinversion:allsixbasicfocalmechanisms,1,2,...6;DC+CLVD+VOL

deviatoricMTinversion:basicfocalmechanisms1,2,...5;DC+CLVD;VOL%=0;

DCconstrainedMTinversion:DConly;VOL%=CLVD%=0

knownandfixedDCmomenttensor(onlypositionandtimeissearched)

Opposedtostrike,dip,rakeandMo,theDC%isstronglyunstable.Itcloselyrelates

withthefactthata largedeviationfrompureDChas,asarule,averysmalleffect

upontheseismograms.Indeed,itcanbedemonstratedbymanyexamplesinwhich

syntheticsfor,sayDC%=50andDC%=100,cannotbedistinguishedbyeyefromeach

other, andquantitativemeasureof their fitwith realdata isnearly identical (e.g.

variancereduction,introducedbelow,differsby1%).Therefore,wecansaythatthe

DC%valueprovidedbytheroutinemomenttensorinversionisrarelyofanyphysical

meaning.ThesameappliesforthevolumepercentageVOL%.

Optionally,theinversioncanbeconstrainedthroughtheLagrangemultiplierstogive

anearly100%DCsolution.The(nonlinear)conditionthatthemomenttensormust

havezerovalueddeterminantissolvediteratively.Itslowsdownthecalculationand

maycreateproblems.Thereisnospecialadvantageinthisoption,becausethestrike,

dip and rake of the DCconstrained solution is usually very near to that of the

(unconstrained)deviatoricMTinversion.

Thus themost recommended inversionmode is deviatoric inversion (VOL%=0) in

which,however,theresultingDC%isconsideredwithgreatcaution.

Itisassumedintheaboveexplanationthatthesourcepositionandtimeareknown.

This code allows their optimization through a grid search over set of trial source

positionsandtimeshifts,predefinedbytheuser.Thesearchseeksthetrialsource

position and time for which the residual error of the least square method is

minimized. It is equivalent to maximize correlation between the observed and

syntheticseismograms.Theconceptofoptimizingpositionandtimeisapplicableto

eachpointelement (thesocalledsubevent)ofthegenerallymorecomplexsource

model. If thewhole earthquake is represented (in the lowfrequency range) by a

singlesource,theoptimumsolutionprovidedbythegridsearchcorrespondstothe

centroid(thecentroidposition,centroidtimeandthecentroidMT).

Usercancheck thecorrelationvaluesasa2D functionof the trial sourceposition

andtime.Thecodehasaninteractivepartinwhichusercanuseautomaticsearchof

the optimum correlation, or canmake his preferred choice. The preferred choice

may be the source position or timewith a somewhat lower correlation, close to

formalmaximum, inwhichhoweversomeotherconditions (constraints)arebetter

satisfied. In thisway user can apply, for example, his knowledge about the first

motionpolarities,geologicallydeducedfaultdip,variousassumptionsaboutrupture

propagation,etc.The2Dcorrelationmayalsohelp in identifyingpoorresolutionof

someparameters,forexamplethedowndipsourceposition.

Narrow bandpass inversions around period T can often provide two correlation

maxima,intimetandt+T/2,characterizedbyrakeandrake+180respectively.This

is just the casewhereeven a single guaranteed firstmotionpolaritymayhelp to

decidebetweenpropertime,tort+T/2.

Thecodeworksiteratively.Apointsourcecontributioniscalledsubevent.Usingdata

code searches for subevent 1. Once subevent 1 is found, its contribution is

subtracted from the data to get the socalled residual data. In the next step the

residualdataareprocessedinthesamewayastheoriginaldataduringthefirststep.

Subevent2 is found,etc.Originaldataminus the lastresidualseismogramprovide

theresultingsyntheticseismogram.

Optionally, the search of spatial and temporal distribution of subevents can be

performedwithfixed(100%DC)momenttensor.Theuserprescribestheknown(or

assumed)strike,dipand rake,and thesevaluesarekept fixed forallsubevents. It

can be recommended when the unconstrained moment tensors vary chaotically

fromonesubeventtotheother.

Whenthesolutionisrepresentedbyseveralsubeventsofdifferentfocalmechanism,

theresultingscalarmomentcannotbeobtainedasthesumofthesubeventscalar

moments. That is why we also provide an output file where, subsequently, the

subevent contributions are summed up as tensors and the scalarmoment of the

resulting(cumulative)tensorisshown.

Denotingdataasd,andsyntheticsass,thefitbetweenthemismeasuredbytheso

calledvariance reductionvarred=1 |ds|2/|d|2,where|.|denotes theL2norm,

e.g.,|d|2=suma(di2).Thenormiscalculatedasasinglenumbersummingupoverall

time series, all components, and all stations. The optimum value of varred is 1.

Wrongsyntheticsmaygiveevenvarred

the code calculates varred using d and s=s1+s2, i.e. varred= 1 |d(s1+s2)|2/|d|2.

Obviously,thevarredvaluereportedafterthesecondsubevent isnotthesameas

the (squared) correlationbetween r and s2.Moreover, this varred is alsonot the

sameasthe(squared)correlationbetweendands=s1+s2,becausewedidnotfind

thesynthetics=s1+s2byasingleleastsquareminimizationof|d(s1+s2)|.

When nonunit weights are used, and/or some stations are deselected from a

particular inversion run, the relation between correlation and variance reduction

getsevenmorecomplicated.

RunningtheGUI

Inordertorunthecode,withintheMatlabcommandwindow,changedirectory(i.e.

usingthecdcommand inMatlabcommandwindow)tothefolderyouwanttorun

theGUIandtype isola.ThiswillrunthemainGUI fileandaftersome initialization

messagesyoushouldgetaformlikethefollowing(Fig.1).

Figure1.MainformoftheISOLAMatlabGUI.

When ISOLAGUI startswithina folderchecks if ISOLAGUI specific subfoldersare

present, ifnot itstartstocreatethemonebyone.Additionally itcopies*.stnand

*.cru files it finds in ISOLAGUI installation folder to the current run folder.Files

withextension*.stnarestationcoordinatesfileswhile*.crufilesarecrustalmodel

files. It is a nice practice to have such files that you use often in ISOLAGUI

installationfolder.UponstartISOLAGUIwillcopythesefilesandthusiftheuserhas

afewcrustalmodelsthatusesoftenthesewillbeimmediatelyavailablewithoutthe

needtobrowseforthefilethroughvariousfolders.Furthermore,theGUIwillsearch

underinstallationfoldertofindafoldernamedPZFILESifpresentitwillcopyallfiles

in installation folder\PZFILES folderunder the run folder\PZFILES, ifnot itwillask

theuserwheretofindthepoleandzerofiles.

CrustalModel

Thefirststepintheinversionprocedureisthedefinitionofthecrustalmodel.Thisis

done by pressing the Define Crustal Model button in themain form,whichwill

launchtheformshowninFig.2.Thereisafixedoptionforamaximumof15layersin

thecrustalmodel.Foreachlayer,theusershouldgivethedepthofthelayertop,the

Vp,Vsvelocitiesinkm/sec,densitying/cm3,Qp,Qsand,optionally,atitle.Inorder

toallowtheprogramtounderstandthe last layer,theusershouldtype999 inthe

lastrowasshowninFig.2.

Therearebuttonsforsavingthedata(Save) inatextformatfilesuitablefor ISOLA

Fortrancode,aswellas reading itback in the form (Read).The latter isuseful for

editingapreviouslysavedmodel.Theplottingoption(Plot)generatesgraphsofVp

and Vs versus depth. Automatic calculation of Vs according to a specified Vp/Vs

value is also possible, aswell as the calculation of density according to formula

density (g/cm3)=1.7+0.2*Vp (km/s).PressingSavethecrustalmodel filethatwas

createdissavedundertheGREENandPOLARITYfolders.

Figure2.TheCrustalmodeldefinitionform.

ThenativeformatofthecrustalmodelfileinISOLAFortrancodeisthefollowing:

Crustal model Tomography model number of layers 8 Parameters of the layers depth of layer top(km) Vp(km/s) Vs(km/s) Rho(g/cm**3) Qp Qs 0.0 5.47 2.700 2.560 300 300 2.0 5.50 2.860 2.800 300 300 5.0 6.00 3.230 2.940 300 300 10.0 6.20 3.240 2.940 300 300 15.0 6.48 3.400 2.980 300 300 20.0 6.70 3.800 2.980 300 300 30.0 6.75 3.810 2.980 300 300 40.0 8.00 4.660 3.360 1000 1000 ************************************************************************* Afterfinishingwiththecrustalmodelitistimefortheusertogivesomeinformation

relatedtotheeventhewantstoanalyze;this isdonebypressingEvent Info inthe

mainform(Fig.3)

EventInfo In this form theuserprovides informationthatwillbeused inall thesubsequent

stepsof the inversion, like theevent Latitude, Longitude,Depth,Magnitude,Date

(the lasttwoarentused inanycalculationandare included justforclarity),Origin

Timeof theevent,StartTimeof thedata file (seismograms)and, finally, theTime

Lengthofthedatathatwillbeusedfortheinversion.Forusersconvenience,there

are5predefined time length intervals thatshouldcovermostapplicationsat local

andregionaldistances.AfterpressingtheupdatebuttontheGUIwritesorupdates

theappropriate filese.g.event.isl, rawinfo.isl,duration.isl; thoseare ISOLA (*.isl)

related text files thathold theabove informationandare stored in ISOLA running

folder.

Figure3.TheEventInfoform.

Nextstepistheselectionofthestationsthatwillbeusedfortheinversion(Fig.4).

StationSelection

Figure4.TheStationSelectionform.

Optionsinthisformaresimple;theusershouldpressMakeMapSelectstationsin

order to select his (previously prepared) text file containing the geographical

coordinatesof thenetwork. Thename and locationof the file isdisplayed at the

SelectedStationFilesection.TheGUIwillselectthefileautomatically, ifafilewith

*.stnextensionexists in ISOLA installation folder. Iftheuserwantstochange ithe

can browse to select a different file. The file should be an ascii file with three

columns, Station Name, Latitude, Longitude, separated by spaces without any

header.TheStationNameshouldhave3characters.Ifitislongerawarningisissued

andthestationnameisreducedtothefirstthreecharacters,cautionisneededsince

stationnameslikeforexample,ABCD,ABCFwillresultinthesamestationnamefor

both,ABC, causingproblems.PressingMakeMap Select stations (and assuming

thatM_MAP isproperly installed)amapof thestationdistribution iscreated,and

theusercanselectthestationshewantstoincludeintheinversion.Selectionofthe

stationsisdoneusingtheleftmousebutton;thelaststationshouldbepickedusing

the rightmousebutton.Afterpressing the rightmousebuttonawarningwindow

comesupwiththetotalnumberoftheselectedstations.Laterduringthe inversion

stage,ifnecessary,theusercanagaindeselectsomestations,i.e.toremovethem

from the inversion process, but once the station was selected the corresponding

seismogramsmustbeprovided.

* Sometimeswhen stations are too close clicking on one of themmay result in

selectionofboth, toavoid this,aparameterhasbeenadded (defaultvalue0.1) in

Stationselectformadjustingthis(makingsmaller)couldremovetheaboveproblem.

After finishing the selectionof the stations theuser should justpress Exiton the

Station Selection form. Doing this the GUI will create files like stations.isl,

station.dat,source.dat(inGREENfolder)andallstat.datinINVERTfolder.

RawDataPreparation

NextstepistheRawDataPreparation(Fig.5),maybethemostimportantoptionof

theGUI,sinceitprocessestheseismograms(doingtheinstrumentcorrection,origin

time alignment, resampling) and produces data files ready for the inversion. The

data,i.e.theuncorrectedseismograms,mustbeavailablein4columntextfiles(with

the strictly required column order, i.e., Time in seconds , NS, EW, Z in counts,

separated with spaces), one file per station. The filenames are not completely

arbitrary;theyhavetostartwiththestationname,forexample,fortheLTKstation

thefilenamemuststartwiththe lettersLTK,whereLTK isthestationnameused in

theStationSelection.Theremainingpartofthefilename(includingtheextension)is

arbitrary,the locationofthefile isalsoarbitraryanduserwillbeguidedtobrowse

forfiles.

*** ISOLAGUI has some default folder for storing the uncorrected files it is the

\datafolderandthefilesifcreatedusingtheISOLAGUItools(e.g.sacimport)havethefollowingfilenamee.g.LTKunc.dat.

Theusershouldalsomakeavailablethefilescontainingtheparametersthatwillbe

usedfortheinstrumentcorrection.Anexampleofsuchapoleandzerofilefollows.

A few pole and zero files for several instruments are includedwith the software

distributionandthenewGUIversionhasatoolforpreparingthesefiles(makepz).

A0 Comment133310 A0valuecount>m/sec Comment3.33e10 conversioncountstom/seczeroes(ReandIminrad/sec) Comment3 Numberofzeroes0.00.0 Zero0.00.0 Zero51.50.0 Zeropoles(ReandIminrad/sec) Comment5 NumberofPoles272218 Pole272218 Pole56.50 Pole0.11110.1111 Pole0.11110.1111 Pole

Itisstrictlyrequiredthatthefiledescribestheinstrumenttransferfunctionforinput

velocity.ThefilenamemustbeacombinationoftheStationNameandtheBH*.pz

string; forexample, for thestationnamedLTKand theEWcomponent, itmustbe

LTKBHE.pz,thusthreepoleandzerofilesperstation,areneeded.Thelocationofthe

pzfiles isnotarbitrary, theusermustplace them in thePZFILES folder.Caution

mustbegiventotheappropriateunits.ISOLAneedsthepolesandzerosinrad/sec,

andtheconstantofthetransferfunctionA0(guaranteeingthattheplateauofthe

amplituderesponseequalstounity),shouldbeconsistentwiththat.Incasethatthe

user has the zeros and poles in Hz, they all must be multiplied by 2, and,

correspondingly,A0mustbemultipliedby(2)NPNZ,whereNPandNZisthenumber

ofthepolesandzeros,respectively.

Figure5.TheDataPreparationform.

PressingLoadAscii file,astandardopen filedialogappearsand theuserselectsa

datafile.Whenthefileisread,thesamplingfrequencyisdisplayed(inred)atthetop

oftheform(Fig.5),sidebysidewiththeresamplingfrequencyofthedata inblue.

The resampling ismade automatically,basedon specificmethodical requirements

andtheeventinfoinputfromtheprevioussteps.

AfterdataloadingtheCutandInstrumentcorrectionbuttonsareenabled.Ifnotall

of the data is neededusing the Cut button the last part of it can be deleted.By

pressingtheInst.Correctionbuttontheprogramsearches inPZFILESfolderforthe

appropriatepoleandzerofileandthenperformsthe instrumentcorrection.During

thisoperationafiltercanbeapplied(Butterworth,2ndorder,zerophase)alongwith

the DC and trend removal, all using the builtin Matlab functions. The baseline

optionisanalternativeoftheDCremoval,inwhichthebaselineisdeterminedfrom

thebeginningoftheseismogramonly.

Next step is the time alignmentof the seismogram, i.e., irrespectivelyof its Start

Time,sincenowitwillbeginattheearthquakeOriginTime;thisisdonebypressing

theOriginAlignbuttonwhichbecomesactiveaftertheinstrumentcorrection.

Finally the user should press the Save Data button in order to save the files in

INVERTfolder.Thefilesaresavedastextfiles(4columns,Timeinsec,NS,EW,Zin

m/sec),onepera station,always containing just8192pointsof theappropriately

resampleddata.TheGUIautomaticallycreatestheproperfilenameforthecorrected

resampleddata,whichforstationLTKwouldbeLTKraw.dat.Thisfilenamemustnot

bechangedbytheusersinceitwillbeusedintheinversionstep.

TrialSourceDefinition

The finaldata that theuser shouldprepare is the trial source location and this is

donebypressingtheSeismicSourceDefinitionbuttonintheISOLAmainform.The

userhastoselectsinglesourceormultiplesourcedefinition.

Inthecaseofsinglesource(Sourcesbelowepicenter),hecanvarythedepthonly,

thustheoptionsintheformareStartingdepth,DepthstepandNoofSources,the

explanationofwhich isgiven inFig.6. Inthiscase,allthetrialpositionsarebelow

theepicenter.BypressingExit theprogramwrites theappropriate files inGREEN

andGMTFILES folders. These files are src*.dat files inGREEN and sources.gmt in

GMTFILES.Thesources.gmtfileisformattedforGMT(psxy)plotting.

It isassumedthatthesinglesourceoptionwillbealwaysusedtoretrieve (ateach

trial depth) just a single subevent, that one which predominates in the low

frequency inversion. The grid search over the depth then serves to provide the

optimumsourcepositioncharacterizedbythebest fitbetweenthewaveformdata

and synthetics. Thus we get a first approximation of the centroid. By the first

approximationwemeanthat(opposedtoassumptionofthisoption)thecentroidis

notnecessarilybelowtheepicenter.

Figure6.TheSingleSourcedefinitionform.

AspecialcaseofsinglesourceinversionistheOneSourceatHypocenterwherejust

onesourceisusedfortheinversion,theonethatislocatedatthehypocenter.

IftheuserwishestousetheMultipleSourceinversionanewformappears(Fig.7).

Thisinversionhasthreeoptions:sourcesalongthestrikeofthefault,sourcesalong

thedip,or sourcesonaplane.Theuserhas to select the fault strikeanddip, the

number of the trial sources he wants to try, their spacing, and the first source

Starting Depth

Depth step

position.AfterpressingtheCalculatebuttontheprogramwritesthesource files in

GREENfolderandproducesamapwiththetrialsourcedistribution.

TheMultipleSourceoptionhastwodifferentapplications.Thefirstoneistoprepare

trialpositionsforthegridsearchofthecentroid, inspectingusuallypositions inthe

vicinity of the optimum depth found with the single source inversion. In this

applicationwedodesignamultiplesourcestencil,butmake inversion insuch low

frequencies that just a single subevent represents thewhole source. The second

possible application of the multiple source option is to design the trial source

positionsforinversionoftheearthquakeintoacomplexsourcemodel,consistingof

more than a single subevent. Obviously, as a rule, the latter is achieved by the

inversion includinghigher frequenciesandusingadensergridofthetrialpositions

thanofthefirstapplication.

Wehavetonoteherethatthismanualdescribesthecodeusageandcodeoptions.It

cannotdescribeallpossiblestrategieshow touse thecode.Forexample, theuser

mayusethemultiplesourceoptioninthebeginningofhisstudytofindthecentroid

(the first application), which might need trial positions relatively far from the

hypocenter,andwitharelativelylargegridspacing.Thenhemaywishtorepeatthe

sameprocedurewith finergrid spacing to find theexactpositionof the centroid.

Finally, he can try the application of the second type, i.e. to resolve several

subevents. The lattermay often fail, due to lacking data, or simply because the

earthquakehasnoclearcomplexity, thenhis result remains tobe just theprecise

centroidsolution(withnoadditionaldetails).Thisdiscussionexplainswhyitisnearly

impossible to give an alwaysworking hint ofwhere and how densely the trial

sourcepositionsshouldbedesigned.

1

2

3

5

4

6

S tr ike }Spac ing

Ne w Hypoc ente r a t so urc e 1

Sh ift to E a st

Shift

to N

orth

H ypo ce nte r

Figure7.TheMultipleSourcedefinitionform.

GreenFunctionComputation

After finishingwith the trial sourcedefinition the inversion can startand the first

step is to prepare theGreen functions. This is done by pressingGreen Function

Computation in the ISOLAmain form.Thegreenpre.m is running (Fig.8)and, for

simplicity,theuserhasonlyoneoptiontofill in,this isthemaximumfrequencyof

theGreen functions tobe computed (fmax). (Obviously,nohigher frequency than

thisonecanberequestedlaterintheinversion.)PressingRunthenecessaryfilesare

created inGREEN folderandtheexecutableFortrancodesarecalled fromMatlab:

gr_xyz.exe and elemse.exe, for the Green function and elementary seismograms

computation, respectively. The execution is monitored through the systems

CommandWindow.Theuser shouldwatch theexecutionof theFortranprograms

andpressOK in the Copy files in invert folderdialog,onlywhen theprocedure

ends in theCommandWindow, a relevantmessagewill appear there.After that,

copying startsandamessage is issuedwhen the filesarecopied in INVERT folder

andtheusercanproceedtotheinversion.

Forsimplicity,thisversionofthecodedoesnotspecifyanyparticularslipratetime

function. Itmeans that the assumed slip rate is that givenby theGreen function

calculation. By definition, the Green function is response of the medium to the

impulsive(Diracdeltafunction)source,butnotethatweworkinalimitedfrequency

band.Therefore,workingwith thebandlimiteddelta function, theactual sliprate

function applied in the code has duration approximately equal to dur=1/fmax,

wherefmaxisthemaximumfrequencyconsideredintheinversion.Theonlycorrect

applicationofthiscodeisforsubeventswhosetruedurationsareshorterthandur.

Figure8.TheGreenfunctioncomputationform.

Inversion

The laststepstartsbypressing Inversion in the ISOLAmain form; it runs invert.m

thatproducesthefollowingform(Fig.9).

Figure9.TheInversionform.

Beforerunningtheinversion,theuserhastoselecthisoptionsregardingtheFilter,

Type of Inversion,Number of Subevents to be retrieved, and parameters of the

TimeSearch(temporalgridsearchofthesubevents).Thesamefilterisautomatically

usedforthedataandsynthetics.Propervaluesoftheaboveparametersdependon

the specific problem e.g. on the event magnitude, on signal to noise ratio, on

locationuncertaintyetc.Thus it isupon theuser to select thebest values forhis

problem.

The usermay press the Compute weights buttonwhich automatically calculates

weights to be applied in the inversion. (Not pressing this buttonmeans that unit

weightswill be used.) The automaticweights are inversely proportional to peak

valuesofgrounddisplacementofthe individualcomponents intheusedfrequency

band.InfactwhatarecomputedbytheComputeweightsfunctionarejustthepeak

valuesforthetracesandlatterisola.exetakesthe1/peakvalueastheweight.Finally,

pressingRun,themainexecutableFortrancodeisola.exe isrunninginthesystems

Commandwindow(Fig.10).Whenfinishingwiththefistsubeventretrieval,thecode

makesapauseandaskstheusertoaccepttheautomaticselectionofthetrialsource

position(thatofmaximumcorrelation),ortoselectsomeotheruserspreferredtrial

source position. To simplify the decision, the user can plot a correlation diagram

usingthePlotCorrelationoption(Fig.11);GMTandGsviewareneededforthisplot.

Inthis2Ddiagramthecorrelationvalueandfocalmechanismareplottedagainstthe

trialsourcepositionandtimeshiftforthesubeventunderstudy.

PressingtheDeselectStationsbutton,theallstat.datfileopensusingnotepad,and

theusercan removeastation from the inversionbyediting thesecondcolumnof

the file (1=use the station, 0=not use it). The columns 3, 4, 5 contain the above

mentionedpeakdisplacementvaluesfortheNS,EW,Zcomponent,respectively.The

user canmanually edit them, thusmaking his preferred specification ofweights.

Notethatthelargerthenumberinallstat.dat,theloweristheweight.

SeealsotheMethodchaptertolearnmoreabouttheweightsandcorrelation.

Allstat.datfileexampleincludingweights.

GUR16.057019e0052.130505e0043.082369e004

LTK16.179501e0052.366762e0042.285469e004

DID11.139388e0041.451932e0041.765126e004

PYL11.145303e0041.020548e0041.030644e004

Figure10.Exampleoftheinversionrun.

Figure11.Exampleofthecorrelationplot.

Plotting

The inversion code isola.exe createsanumberofoutput files that canbeplotted

after the inversion run. This isdonebypressingPlot Resultsbutton on themain

ISOLA form. The plotres.m is called and produces the form of Fig. 12. There are

options for plotting Synthetic versus Real data, the MT results, as well as for

comparingthesolutionwithfirstmotionpolarities.

TheMT(momenttensor)plottingisdoneusingGMT,andtheuserhastheoptionfor

a single source summaryplot (Fig.13)aplotofCorrelationversusSourcenumber

andDC%(Fig.14)ormultiplesourceresultsplotinmapview,pressingPlotSources.

In all the plots (except the one in the single source summary) the fault plane

solutions are displayed by beach balls without showing the nonDC component,

because,asexplainedabove,thenonDCpartisusuallyunstable.

Notethatthesinglesourceplottingoption isavailablealso forthe inversionwhich

resulted in more than one subevent. The code prompts the user to specify the

subevent he wishes to plot in Fig. 13 and Fig. 14, and only this is plotted. The

variance reduction given in the Single Source plot in Fig. 13 then, refers to the

situationafteraddingthechosensubevent(forexample,whenplottingsubevent2,

thevarredvalueapplies for the fitbetweendataand the synthetics composedof

subevent 1 and subevent 2). The fit is calculated only from stations used in the

inversion(thedeselectedstationsarenotconsidered).

Figure12.ThePlottingform

PressingthePlotSourcesbuttontheplsource.mopens.ThiscreatestheformofFig.

15.Theuserhasalotofoptionsinordertocreateamapwiththemultiplesubevent

results (Fig.16).Mostof theoptionsare selfexplanatory,but someknowledgeof

GMT isneeded.Themostcriticalare theBeachballshiftandBeachballXshift to

preventoverlappingofthebeachballs.Theplotformally includesallthecalculated

subeventsbutlotofcareisneededtofindoutwhichofthemarephysicallyjustified.

Thiscomplicatedphysicalproblemisnotsolvedhereinthemanual.See,forexample,

Zahradniketal.(2005).

Figure13.TheSinglesourcesummaryplot

Figure14.TheCorrelationvsSourcenumberplot.

Figure15.Themultiplesourceplottingform.

Figure16.Plotofthemultiplesourceinversionresults.

Fullnumerical resultsof the inversion are available in the files inv1.dat, inv2.dat,

inv2c.dat, inv3.dat, inv4.dat, located in the INVERT folder. For a detailed

explanation, the readme filesof the ISOLAFortranguide shouldbeconsulted (see

below).Mostoften,simpleroutput(thatprovidedinthePlottingform)issufficient.

FinallytheuserhastheoptiontoplottheMT inversionresultsalongwithselected

polarities(Fig.17) inordertocheckvalidityofthe inversion.Afewfilesneedtobe

updated for thisoption.Namely the station.dat filehas tobemanuallyedited to

assign the observed polarities per stations. This can be done within the GUI by

pressing Input Polarities afterwhich the station.dat file opens in an editor. The

other two files thatneed tobe createdareonemech.datandmoremech.dat that

theuserhastocreateinthePOLARITYfolder.Theonemech.datcontainsdatatobe

shown in red (e.g. the solution from ISOLA),whilemoremech.dat can include, for

comparison,severalothersolutions(e.g.thosefrominternationalagencies).Thetwo

filescanbeconstructedautomaticallybytheISOLAGUIbypressingEdit*mechfiles,

theGUIwillchecktheINVERTfolderforresults(theINV2.DATfile),preparethetwo

filesbasedonthe inversionresultsandcopythemtoPOLARITYfolder.Then itwill

open the files in an editor and theuser canmake changes ifhewishes, e.g. add

anothersolutioninmoremech.dat.

Figure17.Plotofpolaritieswithinversionresults.

Moremech.datexample(spaceseparatedtextfile;onlycolumns4,5,6=strike,dip,

rakeareimportanthere)

4 6.66 .185761E+18 151. 76. 77. 13. 19. 131. 251. 61. 44. 32. 88.9 .7718E+00 1 3.96 .560486E+17 201. 50. 144. 316. 63. 46. 76. 83. 175. 39. 68.4 .8426E+00

In the new version of ISOLAGUI, there is an option for plotting extra station

polarities, e.g. from short period stations thatwerent used in the inversion but

provide polarity information that can help in constraining the moment tensor

solution. To do this the user should prepare a text file called extrapol.pol in the

POLARITY folder theGUIwillcheck for thepresenceof this fileandadd theextra

polaritiesinthefinalplot.

UtilitiesIandIIBesidestheinversionrelatedtools,anumberofoptionsisprovidedforassistingthe

user in converting his binary data to ISOLA ascii format and inspecting the data

quality.Toolsareavailablefor importingdata intwoformats:SACandGCF(Guralp

Compressed Format). The tools are quite easy to handle; just read the files,

componentbycomponent,andthensavethefile(Fig.18).Ifthethreecomponents

at a station dont share the same starting time, or dont have the same length,

optionsfortheirtrimmingareprovided.

Figure18.TheGCFfileimportform.

Thetoolsfor importingdataarebasedonfreeMatlabroutinesfromtheWeb(see

acknowledgmentpartofthemanual).Theusercanusethemasanexampletoeasily

addhispreferredformatconversiontothepresentGUI.

AfterconvertingthedatatoISOLAformattheuserhastheoptiontoinspectthedata

qualityeitherusingtheInspectDatatoolortheTryFilterstool.Datacanbefiltered

invariousfrequencybandsinordertodefinetheproperbandforinversion(i.e.the

band with a good signaltonoise ratio). Data can be also inspected as the

displacement. It is extremely important to inspect the displacement without

filtrationandinstrumentcorrectionsinceitallowsdetectionofvariousdisturbances

thatareoftenhiddeninthevelocityrecordsand/orinthedisplacementbandpassed

records(ZahradnikandPlesinger,2005).

FinallythedatacanbeshiftedusingtheShiftdataoption.Thisoptionmaybeused

(withgreat caution)when, forexample,wehavean indication that theemployed

crustalmodelisnotappropriateatsomestationasregardsthearrivaltime.

AnewmemberoftheUtilitiescodesismakepz.ThisisaGUIthatwillassisttheuser

toprepareapoleandzero file for ISOLA. Itsuse isverysimple, theuserneeds to

presstheNewZeroandNewPolebuttonstoaddthepropernumberofpolesand

zerosforhissystem.Thenhehastoaddallthepropernumbersinthetextboxesand

finally save them in a file suitable for ISOLA, by pressing Save file. The GUIwill

proposeaproper filenamebasedontheStationnamegivenandtheusercanalso

plottheresponsecurvebypressingPlot.

Figure19.ThemakepzGUI.

AcknowledgmentsSpecialthanksgotoPetraAdamovaforextensivetestingofISOLAGUI.Thefollowing

mfilesarepartofotherprogramsthatwefoundusefulandaddedtotheGUI.

rsac.m,lh.mbyMichaelThorne, readgcffile.mbyM.McGowan,GuralpSystemsLtd., Bandpass.mCoraldistribution.

In the Fortran part, several subroutineswere used,written by other authors:M.

Bouchon,O.Coutant,J.Sileny,J.JanskyandO.Novotny,J.A.Snoke,P.Reasenberg

andD.Oppenheimer.Codes from FortranNumericalRecipeswerealsoused.This

workwas supported by the EC project 0040433HAZCorinth and by the Charles

UniversityinPraguegrant,GAUK279/2006/BGEO/MFF.

Appendix I - How to prepare a pole and zero file for ISOLA. Preparingaproperpoleandzero filehasalwaysbeenaproblem.Thuswe try

heretogiveanexampleonhowtoprepareacorrectpoleandzerofileforISOLA.

The format of the file is not discussed here since it is described in the ISOLA

manual.Inthisdocumentthecorrectproceduretocomputethepropervaluesis

escribed.d

ThusinordertoprepareapoleandzerofileforusewithISOLAweneedtoknow

hefollowing:t

ISOLAneedsthepoleandzerovaluesinrad/s. The pole and zero should describe the VELOCITY response of the

instrument

nsetooTheA0valueshouldbegivenforVELOCITYrespo Besides theA0weneed toprovide thevalueofm/secthatequalsto1

count.

Before proceeding with instrument correction we can use option PlotResponse(fromRawdataPreparationGUI)thiswillplotthe instrument

response of the instrument, (Fig.1). At this plot we should check if the

frequencyrangeofflatresponseisthecorrectoneandiftheamplitudeof

theresponsefunctionisone,thismeansthatourA0valueiscorrect.

WepresenttheaboveusingtheexampleofaTrilliumseismometerandaTrident

(Nanometrics, http://www.nanometrics.ca/) digitizer. From the manual we

knowthefollowing:

AndTridentissetatthe1cou

huswehavethefollowing:

ntpermicrovoltsensitivity.

T

A

0=133310

Using the Trillium sensitivity (1500 V/m/sec) and digitizers sensitivity

1cnt/microV)wegetthevalue6.66667e10asm/secper1count.(

inallyweputtheabovevaluesinatextfilewiththefollowingformat.F

A0

133310

count>m/sec

6.6667e10

zeroes

3

0.00.0

0.00.0

51.50.0

poles

5

272218

272218

56.50

0.11110.1111

0.11110.1111

Example of Pole and Zero file for ISOLA (Trillium40 seismometer and Trident

digitizer)

igure1.FrequencyResponseforTrillium40seismometer.F

What do ifyouhaveaRESPfile.

If the user has his response info in SEED RESP format, creating an ISOLA pole

zero file is easy. First search for the B053F07 A0 normalization factor: entry, this is

your A0 value. Then copy the pole-zero part from RESP file to ISOLA pole zero file,

the values are exactly the same but BE CAREFUL to have the RESP file for input

velocity since this is needed for ISOLA. Finally search for the B058F04 Sensitivity:

to

entry, this value is the inverse of the value needed by ISOLA to specify sensitivity,

thus the inverse of this number should be put in ISOLA pole zero file in the

ount>m/secoption.c

Appendix II: Files and folders

In this sectionexamplesof filesareprovidedaccording to the folders theyare

ocated.l

\

herootrunningfolder,shouldcontainfileslike*.isl,*.stn,*.cru.T

\data

hisfoldershouldcontainuncorrecteddatainISOLAformat(4columnasciifiles)T

\gmtfiles

FilesforplottingwithGMTaresavedhere,bothdatafilesandbatchfilesusedfor

the calling of GMT commands e.g. event.gmt, sources.gmt, psources.bat,

lotselsta.batetc.Moreover*.kmlfilesforusewithGoogleEartharesavedhere.p

\green

ilesusedinGreenfunctioncomputation.F

\invert

ilesusedforinversionandinversionresults.F

\output

raphicsfiles,*.pngaresavedhere.G

What is new in ver. 4.0 ?GUI PurposeRequirementsInstallationMethodRunning the GUICrustal ModelEvent InfoStation SelectionRaw Data PreparationTrial Source DefinitionGreen Function Computation InversionPlottingUtilities I and II

AcknowledgmentsAppendix I - How to prepare a pole and zero file for ISOLA.Appendix II: Files and folders