简介：Irregularsurfaceflattening,whichisbasedonaboundaryconforminggridandthetransformationbetweencurvilinearandCartesiancoordinatesystems,isamathematicalmethodthatcanelegantlyhandleirregularsurfaces,buthasbeenlimitedtoobtainingfirstarrivalsonly.Bycombiningamultistageschemewiththefast-sweepingmethod(FSM,themethodtoobtainfirst-arrivaltraveltimeincurvilinearcoordinates),thereflectedwavesfromacrustalinterfacecanbetracedinatopographicmodel,inwhichthereflectedwavefrontisobtainedbyreinitializingtraveltimesintheinterfaceforupwindbranches.Alocaltriangulationisappliedtomakeaconnectionbetweenvelocityandinterfacenodes.Thenajointinversionoffirst-arrivalandreflectiontraveltimesforimagingseismicvelocitystructuresincomplexterrainsispresented.Numericalexamplesallperformwellwithdifferentseismicvelocitymodels.Theincreasingtopographiccomplexityandevenuseofahighcurvaturereflectorinthesemodelsdemonstratethereliability,accuracyandrobustnessofthenewworkingscheme;checkerboardtestingillustratesthemethod’shighresolution.Noisetolerancetestingindicatesthemethod’sabilitytoyieldpracticaltraveltimetomography.Furtherdevelopmentofthemultistageschemewillallowotherlaterarrivalstobetracedandusedinthetraveltimeinversion.

简介：OnNovember13,2016,anMW7.8earthquakestruckKaikourainSouthIslandofNewZealand.Bymeansofback-projectionofarrayrecordings,ASTFs-analysisofglobalseismicrecordings,andjointinversionofglobalseismicdataandco-seismicInSARdata,weinvestigatedcomplexityoftheearthquakesource.Theresultshowsthatthe2016MW7.8Kaikouraearthquakerupturedabout100sunilaterallyfromsouthtonortheast(~N28°–33°E),producingaruptureareaabout160kmlongandabout50kmwideandreleasingscalarmoment1.01×1021Nm.Inparticular,theruptureareaconsistedoftwoslipasperities,withoneclosetotheinitialrupturepointhavingamaximalslipvalue~6.9mwhiletheotherfarawayinthenortheasthavingamaximalslipvalue~9.3m.Thefirstasperityslippedforabout65sandthesecondonestarted40safterthefirstonehadinitiated.Thetwoslippedsimultaneouslyforabout25s.Furthermore,thefirsthadanearlythrustslipwhilethesecondhadboththrustandstrikeslip.Itisinterestingthattherupturevelocitywasnotconstant,andthewholeprocessmaybedividedinto5stagesinwhichthevelocitieswereestimatedtobe1.4km/s,0km/s,2.1km/s,0km/sand1.1km/s,respectively.Thehigh-frequencysourcesdistributednearlyalongtheloweredgeoftherupturearea,thehighfrequencyradiatingmainlyoccurredatlaunchingoftheasperities,anditseemedthatnohigh-frequencyenergywasradiatedwhentherupturingwasgoingtostop.

简介：AtUTC2017-11-1218:18:17,anMw7.3earthquakeoccurredattheborderbetweenIranandIraq(location34.886°N,45.941°E,depth23kmaccordingtoUSGS).WecarriedoutfocalmechanismandruptureprocessstudieswiththedatafromIRISdatacenter,using26far-fieldP-waveformsand25SH-waveformswithhighS/Nratioandrelativelyevenazimuthcoverage(epicentraldistance)inapointsourcemodeltoinvertforthefocalmechanismsolution;theresult(Figure1)wasusedtoconstructafinitefaultmodelforruptureprocessinversion(YaoandJi,1997;Wangetal.,2008),resultinginapreliminaryslipdistributionofthisearthquake(Figures2-4).Thecalculatedseismicmomentis1.1×1020N·m,Mw=7.3.Themaximumslipisabout700cm.

简介：AtUTC2018-01-1002:51:31,anMw7.6earthquakeoccurred44kmeastofGreatSwanIsland,Honduras(location17.469°N,83.520°W,depth10km,accordingtotheUnitedStatesGeologicalSurvey).Wecarriedoutstudiesofthefocalmechanismandruptureprocessoftheearthquake,usingseismicdatafromtheIRISdatacenter.Forthefocalmechanismsolution,apointsourcemodelwasusedtoinvert26far-fieldP-waveformsand26SHwaveformswithhighS/Nratioandrelativelyevenazimuthcoverage(epicentraldistance30°<△<90°);thentheresult(Figure1)wasusedtoconstructafinitefaultmodelforruptureprocessinversion(YaoZXandJiC,1997;WangWMetal.,2008),resultinginapreliminarymodeloftheslipdistributionofthisearthquake(Figures2–4).Thecalculatedseismicmomentis2.41×10^20N·mandtheestimatedearthquakemagnitudeMw=7.5.Themaximumslipisabout1900cm.

简介：DataobtainedbyGRACE(GravityRecoveryandClimateExperiment)havebeenusedtoinvertfortheseismicsourceparametersofmegathrustearthquakesundertheassumptionofeitheruniformslipoveranentirefaultorapoint-likeseismicsource.Herein,wefurtherextendtheinversionofGRACElong-wavelengthgravitychangestoheterogeneousslipdistributionsduringthe2011Tohokuearthquakeusingthreefaultmodels:(I)aconstant-strikeandconstant-dipfault,(II)avariabledipfault,and(III)arealisticallyvaryingstrikefault.Byremovingthepost-seismicsignalfromthetimeseries,andtakingtheeffectofoceanwaterredistributionintoaccount,weinvertforslipmodelsI,II,andIIIusingco-seismicgravitychangesmeasuredbyGRACE,de-stripedbyDDK3decorrelationfilter.Thetotalseismicmomentsofourslipmodels,withrespectivevaluesof4.9×1022Nm,5.1×1022Nm,and5.0×1022Nm,aresmallerthanthoseobtainedbyotherstudiesrelyingonGRACEdata.Theresultingcentroidsarealsolocatedatgreaterdepths(20km,19.8km,and17.4km,respectively).BycombiningonshoreGPS,GPS-Acoustic,andGRACEdata,weobtainajointlyinvertedslipmodelwithaseismicmomentof4.8×1022Nm,whichislargerthantheseismicmomentobtainedusingonlytheGPSdisplacements.Weshowthattheslipinvertedfromlowdegreespace-bornegravimetricdata,whichcontainsinformationattheoceanregion,isaffectedbythestrikeofthearcuatetrench.Thespace-bornegravimetricdatahelpusconstrainthesourceparametersofamegathrustearthquakewithintheframeofheterogeneousslipmodels.