简介:3-DS-waveQstructureinJiashiearthquakeregionisinvertedbasedontheattenuationofseismicwavesrecordedfromearthquakesinthisregionin1998bytheResearchCenterofExplorationGeophysics(RCEG),CSB,andaroughconfigurationofdeepcrustalfaultsintheearthquakeregionispresented.First,amplitudespectraofS-wavesareextractedfrom450carefully-chosenearthquakerecords,calledobservedamplitudespectra.Then,afterinstru-mentalandsiteeffectcorrection,theoreticalamplitudespectraaremadetofitobservedamplitudespectrawithnonlineardampedleast-squaresmethodtogettheobservedtraveltimeoverQ,providedthatearthquakesourcesconformtoBrune¢sdiskdislocationmodel.Finally,by3-Draytracingmethod,theoreticaltraveltimeoverQismadetofitobservedtraveltimeoverQwithnonlineardampedleast-squaresmethod.Inthecourseoffitting,thevelocitymodel,whichisobtainedby3-Dtraveltimetomography,remainsunchanged,whileonlyQmodelismodified.Whenfittingcametothegivenaccuracy,theultimateQmodelisobtained.TheresultshowsthatanNE-trendinglowQzoneexistsatthedepthsof10~18km,andanNW-trendinglowQzoneexistsatthedepthsof12~18km.TheseroughlycoincidewiththeNE-trendingandtheNW-trendinglowvelocityzonesrevealedbyotherscientists.ThedifferenceisthatthelowQzoneshaveawiderrangethanthelowvelocityzones.
简介:TwomethodsformeasuringtheattenuationQvalue,frequency-amplituderatiomethodandwaveforminversionmethod,wereanalyzed.Thesizeandshapeofmostrocksamplesinthelaboratorycanhardlyfulfilltherigorousrequirementsoftheabovemethods.AnewtestmethodofusingthewaveenergytocalculatetheQvaluewasproposed.Theprinciple,calculationformulaeandsomepointsforattentionwereexpounded;therelationshipbetweenQ_PandQ_Ewasdiscussed;andmanysamplesweremeasuredbythismethod.Theresultwascomparedwiththosebyothermethods,anditwasconsideredthattheQvaluebythismethodliesbetweenQ_PandQ_E·
简介:Presentaddress:SouthCaliforniaUniversity,USA.ContributionNo.93A0032,InstituteofGeophysics,SSB,China.andstationareseparate,supposingarandomandhomogeneousdistributionofthescattersinathree-dimensionalinfiniteandperfectlyelasticmedium.TheenergydensityatadistanceofrisgivenasE(r,t|ω)=[W0(ω)g0(ω)]/(4πr2).K(vt/r).exp(-ωQc-1t)vt>r(2)WhereK(x)=(1/x)ln[(x+1)/(x-1)],andg0(ω)isthetotalscatteringcoefficientcharacterizingascatteringpowerperunitvolumeofthehomogeneousmedium.Comparisonofvariousobservationsincludingcodadecay?
简介:Basedon49digitalseismogramsrecordedby73seismicstationsintheJiangsuTelemeteredSeismicNetwork,thepaperusesAtkinson'smethodtocalculatetheinelasticattenuationcoefficientoftheJiangsuarea.Wefindthatthefrequency-dependentQintheJiangsuregionisQ(f)=272.1·f~(0.5575).WealsouseMoya'smethodtoinvertthe63stations'siteresponses.Theresultsshowthatthesiteresponsesofthe25stationsinJiangsuareapproximately1atarangebetween1Hzand20Hz,whichisconsistentwiththeirbasementsonrocks.Theresponsecurvesofthesiteresponsesofthe14undergroundstationsaresimilartoeachother.Theirsiteresponsesshowanamplificationatlowfrequenciesandminimizationathighfrequencies.ThecalculationoftheBrunemodelonthewaveformdataofM_L≥2.5earthquakesfromJiangsuDigitalSeismicNetworkbetweenOctober2010andMay2015intermsofseismicsourceparametersof58seismicwavesshowsthattherearegoodcorrelationsbetweenseismicmagnitudeandothersourceparameterssuchasseismicmoment,sourceradiusandcornerfrequency,whilethecorrelationsbetweenseismicmagnitudeandstressdrop,andstressdropandsourceradiusarenotsogood.
简介:Intheestimationofseismictendency,usingGutenberg-Richter¢sb-valueandusingHurstexponentaretwocom-monlyusedmethods.Basedonthefractalgeometryofearthquaketimeseries,wepointoutthatthesetwomethodscorrelatetoeachother.IntheperspectiveoffractionalBrownianmotion(FBM),anearthquakesequencewithb>3/4andthatwithb<3/4havedifferentdynamicproperties.
简介:Basedonisotropiclinearporoelastictheoryandundertheundrainedcondition,wesummarizethreeequationsconnectingtheSkempton’scoefficientBwiththegroundwaterlevel.Afteranalysis,weproposeamethodtocalculatetheSkempton’scoefficientBaccordingtotherelationshipbetweenwaterlevelandtidalstrain.WiththismethodwecangetthevalueofBwithouttheearthquakeoccurrence,whichcanprovidethehighfrequencywavesforresearch.Besides,wecanalsogetthein-suitSkempton’scoefficientBwithouttheexperimentofrockphysics.Inaddition,weanalyzetheobserveddataofChangpingstationrecordedingroundwatermonitoringnetwork(abv.,GMN)beforeandaftertheWenchuanMS8.0withthismethod,andfindoutthere’saslightchangeofthevalueofBaftertheseismicwavespassedby,whichimpliesthatthepropagationofseismicwavesmayhavebroughtsomevariationstotheporoelasticmediumofthewell.
简介:Inthisstudy,weadoptanimprovedBayesianapproachbasedonfree-knotB-splinebasestostudythespatialandtemporaldistributionoftheb-value.SynthetictestsshowthattheimprovedBayesianapproachhasasuperiorperformancecomparedtotheBayesianapproachaswellasthewidelyusedmaximumlikelihoodestimation(MLE)methodinfittingtherealvariationofb-values.WethenapplytheimprovedBayesianapproachtoNorthChinaandfindthattheb-valuehasaclearrelevancetoseismicity.Temporalchangesofb-valuesarealsoinvestigatedintwospecificareasofNorthChina.Weinterpretsharpdecreasesintheb-valuesasusefulmessagesinearthquakehazardanalysis.
简介:TheeffectsofmagnituderoundingandofthepresenceofnoiseintheroundedmagnitudesontheestimationoftheGutenberg–Richterb-valueareexplored,andthewaystocorrectfortheseeffectsareproposed.Fortypicalvalues,b=1androundingintervalDM=0.1,theroundingerrorisapproximately-10-3anditcanbecorrectedtoanegligibleapproximately-10-5.Forthesametypicalvalues,theeffectofnoisecanbelarger,dependingonthecharacteristicsofthenoisedistribution;fornormallydistributednoisewithstandarddeviationr=0.1,thecorrectb-valuemaybeunderestimatedbyafactor*0.97.
简介:AmodelofseismicitywithfractalstructuresandapreliminarydiscussionontherelatiobetweenDandbvalueHat-KunJIANG(蒋海昆)andShou-ZhongDI...
简介:CumulativefrequencybvaluewithoutupperboundmagnitudeanditsregressiondeterminationJian-WenSHEN(沈建文)(SeismologicalBureauofAnhuiP...