简介：ThedatarecordedduringthesitesurveyintheZhangzhouareainFujianProvincebetweenOctober23,2007andDecember3,2007wasanalyzed.Themainmethodsadoptedforthenoiselevelofthisareaarethenoiserootmeansquare(RMS),noisepowerspectrumdensityandnoisecoherencyfunction.Theresultsindicatethatthenoiselevelsofthesurveysitesarehigherinthe1s-10speriods,whichisthemainfrequencybandofpreliminarymicroseism,andalso,twomainnoisesourceswerefoundin1.5Hzandaround5Hz.Accordingtoarithmetic,thedirectionandfrequencybandofthenoisesourcewereanalyzedandacademicproofswerepresented.Atlast,wefoundthatthenoisesourcein1.5Hzwasmadebythewaterwavearousedbythewindinthereservoirregionandthenoisesourcearound5Hzwasmadebythepowerstationinthenortheastdirection

简介：Thenoisedatainverticalcomponentrecordsof85seismicstationsinFujianProvinceduring2012isusedastheresearchobjectinthispaper.Thenoisedataisdividedintofiveminutesegmentstocalculatethepowerspectra.Thehighreferencelineandlowreferencelineofstationarethenidentifiedbydrawingaprobabilitydensityfunctiongraph(PDF)usingthepowerspectralprobabilitydensityfunction.Moreover,accordingtotheanomaliesofPDFgraphsin85seismicstations,theabnormalnoiseisdividedintofourcategories:droppedpacket,lownoise,highnoise,andmediannoiseanomalies.Afterwards,fourselectionmethodsarefoundbythehighorlownoisereferencelineofthestations,andthesystemofreal-timemonitoringofseismicnoiseisformedbycombiningthefourselectionmethods.Noiserecordsof85seismicstationsinFujianProvinceinJuly2013areselectedforverification,andtheresultsshowthattheanomalousnoise-recognitionsystemcouldreacha90%successrateatmoststationsandtheeffectofselectionareverygood.Therefore,itcouldbeappliedtotheseismicnoisereal-timemonitoringinstations.

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：Moststudiesofseismicnoisecross-correlation(NCC)havefocusedonregional/continentalscaleimagingusingempiricalsurface-waveGreen’sfunctionsextractedfromprimary(0.05–0.08Hz)andsecondary(0.1–0.16Hz)microseisms.Inthiswork,wepresenttheNCCresultsathigherfrequencies([0.5Hz)from6monthsseismicnoiserecordedbyalocalarray(*4kmaperture)deployedalongtheCalicofaultintheMojaveDesert,California.BothfastandslowpropagatingwavesareobservedfromtheNCCrecord-sections.WecomparetheNCCsfromsensorpairsthatshareacommonsensorwiththerecordsofaboreholeshotlocatedveryclosetothiscommonsensor.Theresultshowsagoodmatchoftheslowsurface-wavearrivals,indicatingthattheNCCmethodisabletorecoverunbiasedsurface-waveGreen’sfunctionsatlocalscales.Thestrongbody-waveNCCcomponentiscausedbythePwavesgeneratedoffshoreCalifornia.AlongaSW–NEprofileacrossthefault,weobserveapparentP-wavearrivalsandtheirreflections,whichcanbeexplainedbyalow-velocityzone(LVZ)alongtheCalicofault.WecalculatetheLVZwidthtobe*2.3km,andtheP-wavevelocityreductionwithintheLVZtobe*35%.TheseestimatesareconsistentwithotherevidenceforarelativelywideLVZalongtheCalicofault.

简介：TheYellowstonevolcanoisoneofthelargestactivevolcanoesintheworld,anditspotentialhazardsdemanddetailedseismologicalandgeodeticstudies.Previousstudieswithtraveltimetomographyandreceiverfunctionshaverevealedalow-velocitylayerinthecrustbeneaththeYellowstonevolcano,suggestingthepresenceofamagmachamberatdepth.Weuseambientseismicnoisefromregionalseismicstationstoretrieveshort-periodsurfacewavesandthenstudytheshallowshearvelocitystructureoftheYellowstoneregionbysurfacewavedispersionanalysis.WefirstobtainedacrustalmodeloftheareaoutsideoftheYellowstonevolcanoandthenconstructedanabsoluteshearwavevelocitystructureincombinationwithreceiverfunctionresultsforthecrustbeneaththeYellowstonevolcano.Thevelocitymodelshowsalow-velocitylayerwithshearvelocityataround1.3km/s,suggestingthatalarge-scalemagmachamberexistsatshallowlevelswithinthecrustoftheYellowstonevolcanicregion.

简介：

简介：Two-monthcontinuouswaveformsof108broadbandseismicstationsinFujianProvinceanditsadjacentareasareusedtocomputenoisecross-correlationfunction(NCF).ThesignalqualityofNCFisimprovedviatheapplicationoftime-frequencyphaseweightedstacking.TheRayleighandLovewavesgroupvelocitiesbetween1s-20saremeasuredonthesymmetricalcomponentoftheNCFwiththemultiplefiltermethod.Morethan5,000Rayleighwavedispersioncurvesandabout4,000Lovewavedispersioncurvesareobtainedandusedtoinvertforgroupvelocitymaps.Thisdatasetprovidesabout50kmresolutionthatisdemonstratedwithcheckerboardtests.Consideringtheoffgreatcircleeffectininhomogeneousmedium,theraypathistracedbasedonthetraveltimefieldcomputedwithafinitedifferencemethod.Theinvertedgroupvelocitymapsshowgoodcorrelationwiththegeologicalfeaturesintheupperandmiddlecrust.TheFuzhoubasinandZhangzhoubasinshowedlowvelocityontheshortperiodgroupvelocitymaps.Onthelongperiodgroupvelocitymaps,thelowvelocityanomalyinthehighheatflowregionnearZhangzhouandclearvelocitycontrastacrosstheZhenghe-Dapufaults,whichsuggeststhattheZhenghe-Dapufaultmightbeadeepfault.

简介：ThevelocitystructureofthecrustbeneathLiaoningprovinceandtheBohaiseainChinawasimagedusingambientseismicnoiserecordedby73regionalbroadbandstations.Allavailablethree-componenttimeseriesfromthe12-monthspanbetweenJanuaryandDecember2013werecross-correlatedtoyieldempiricalGreen'sfunctionsforRayleighandLovewaves.PhasevelocitydispersioncurvesfortheRayleighwavesandtheLovewavesweremeasuredbyapplyingthefrequencytimeanalysismethod.DispersionmeasurementsoftheRayleighwaveandtheLovewavewerethenutilizedtoconstruct2Dphase-velocitymapsfortheRayleighwaveat8–35speriodsandtheLovewaveat9–32speriods,respectively.BothRayleighandLovephase-velocitymapsshowsignificantlateralvariationsthatarecorrelatedwellwithknowngeologicalfeaturesandtectonicsunitsinthestudyregion.Next,phasedispersioncurvesoftheRayleighwaveandtheLovewaveextractedfromeachcellofthe2DRayleighwaveandLovewavephase-velocitymaps,respectively,wereinvertedsimultaneouslytodeterminethe3Dshearwavevelocitystructures.ThehorizontalshearwavevelocityimagesclearlyandintuitivelyexhibitthattheearthquakeswarmsintheHaichengregionandtheTangshanregionaremainlyclusteredinthetransitionzonebetweenthelow-andhigh-velocityzonesintheuppercrust,coincidingwithfaultzones,andtheirdistributionisverycloselyassociatedwiththesefaults.Theverticalshearwavevelocityimagerevealsthatthelowercrustdownwardtotheuppermostmantleisfeaturedbydistinctlyhighvelocities,withevenahigh-velocitythinnerlayerexistingatthebottomofthelowercrustnearMohoincentralandnortherntheBohaiseaalongtheTanlufault,andthesephenomenacouldbecausedbytheintrusionofmantlematerial,indicatingtheTanlufaultcouldbejustastheuprisingchannelofdeepmaterials.

简介：WestudythefeatureofmediachangesbeneaththeZipingpureservoiranddiscusstheprocessofpermeationwiththewaterlevelriseandfallofthereservoirfromJanuary2005toJanuary2008fromambientnoisecrosscorrelationbyusingcontinuousseismicdatarecordedbythestationsofZipingpuseismicnetworkandYZPstation.Amoving-windowcross-spectrumtechniquehasbeenusedtocalculatetherelativeseismicvelocitychangesbetweenstationpairs.Resultsrevealedanobviousrelationshipbetweenrelativeseismicvelocity,andthewaterlevelchangeswithatimedelaythatmaybecausedbypermeationduringthreemainimpoundmentsandtwolargescaledisemboguements.Impoundmentgeneratesafastandlargeimpactonthesuperficiallayer,andthechangesofseismicvelocityistheresultofincreasedpressureandpermeationduringtheimpoundment.Atthefirstimpoundment,themaineffectfactorispressure.Duringthenexttwoprocessofimpoundment,permeationbecomesthemaineffectfactor,affectingthefaultatadepthofabout8km.

简介：Inhighlypopulatedurbancenters,traditionalseismicsurveysourcescannolongerbeproperlyappliedduetorestrictionsinmoderncivilianlifestyles.Theambientvibrationnoise,includingbothmicroseismsandmicrotremor,thougharegenerallyweakbutavailableanywhereandanytime,canbeanidealsupplementarysourceforconductingseismicsurveysforengineeringseismologyandearthquakeengineering.Thisisfundamentallysupportedbyadvanceddigitalsignalprocessingtechniquesforeffectivelyextractingtheusefulinformationoutfromthenoise.Thus,itcanbeessentiallyregardedasapassiveseismicmethod.Inthispaperwefirstmakeabriefsurveyoftheambientvibrationnoise,followedbyaquicksummaryofdigitalsignalprocessingforpassiveseismicsurveys.ThentheapplicationsofambientnoiseinengineeringseismologyandearthquakeengineeringforurbansettingsareillustratedwithexamplesfromBeijingmetropolitanarea.Forengineeringseismologytheexampleistheassessmentofsiteeffectinalargeareaviamicrotremorobservations.Forearthquakeengineeringtheexampleisforstructuralcharacterizationofatypicalreinforcedconcretehigh-risebuildingusingbackgroundvibrationnoise.Byshowingtheseexampleswearguethattheambientnoisecanbetreatedasanewsourcethatiseconomical,practical,andparticularlyvaluabletoengineeringseismologyandearthquakeengineeringprojectsforseismichazardmitigationinurbanareas.

简介：Wepresenta3DmodelofshearvelocityofcrustanduppermantleinChinaandsurroundingregionsfromsurfacewavetomography.Wecombinedispersionmeasurementsfromambientnoisecorrelationandtraditionalearthquakedata.ThestationsincludetheChinaNationalSeismicNetwork,globalnetworks,andalltheavailablePASSCALstationsintheregionovertheyears.Thecombineddatasetsprovideexcellentdatacoverageoftheregionforsurfacewavemeasurementsfrom8to120s,whichareusedtoinvertfor3Dshearwavevelocitystructureofthecrustanduppermantledowntoabout150km.WealsoderivenewmodelsofthestudyregionforcrustalthicknessandaveragedSvelocitiesforupper,mid,andlowercrustandtheuppermostmantle.Themodelsprovideafundamentaldatasetforunderstandingcontinentaldynamicsandevolution.Thetomographyresultsrevealsignificantfeaturesofcrustanduppermantlestructure,includingmajorbasins,Mohodepthvariation,mantlevelocitycontrastbetweeneasternandwesternNorthChinaCraton,widespreadlow-velocityzoneinmidcrustinmuchoftheTibetanPlateau,andclearvelocitycontrastsofthemantlelithospherebetweennorthandsouthernTibetwithsignificantE–Wvariations.ThelowvelocitystructureintheuppermantleundernorthandeasternTPcorrelateswithsurfacegeologicalboundaries.ApatchofhighvelocityanomalyisfoundundertheeasternpartoftheTP,whichmayindicateintactmantlelithosphere.MantlelithosphereshowsstrikingsystematicchangefromthewesterntoeasternNorthChinaCraton.TheTanluFaultappearstobeamajorlithosphereboundary.