简介:为了核实赤峰1号井2014年初气汞异常现象,安装ATG-6138M测汞仪与原DFG-B测汞仪进行对比观测。ATG-6138M测汞仪观测到赤峰1号井房内空气汞浓度明显高于井孔内逸出汞浓度,表明观测井房可能存在汞污染问题。两台仪器同步观测井孔内逸出气汞浓度结果表明,ATG-6138M测汞仪测试结果稳定,动态清晰,而DFG-B测汞仪观测误差较大。对比DFG-B测汞仪与ATG-6138M测汞仪校准结果认为,DFG-B测汞仪已不能正常观测汞浓度的变化,存在捕汞管老化等仪器问题。综合分析表明,赤峰1号井DFG-B测汞仪存在环境汞污染和仪器老化等因素,且集气装置不符合地震行业标准技术要求,2014年初出现的气汞浓度异常信度不高,不能作为与地震孕育有关的前兆异常信息。
简介:Near-fieldstronggroundmotionsareusefulforengineeringseismologystudiesandseismicdesign,butdenseobservationnetworksofdamagingearthquakesarestillrare.Inthisstudy,basedonthestrong-motiondatafromtheMw6.6Lushanearthquake,thegroundmotionparametersindifferentspatialregionsaresystematicallyanalyzed,andthecontributionsfromdifferenteffects,likethehanging-walleffect,directivityeffect,andattenuationeffectareseparatedtotheextentpossible.DifferentengineeringparametersfromtheobservedgroundmotionsarecomparedwiththelocaldesignresponsespectraandanewattenuationrelationofWesternChina.Generalresultsindicatethatthehighfrequencygroundmotion,likethepeakgroundacceleration,ontwosidesofthefaultplaneissensitivetothehanging-walleffect,whereasthelowfrequencygroundmotion,likethelongperiodspectralacceleration,intherupturepropagationdirectionisaffectedbythedirectivityeffect.Moreover,althoughtheMw6.6Lushanearthquakeisnotalargemagnitudeevent,thespatialdifferenceofgroundmotionisstillobvious;thus,forathrustfaultingearthquake,inadditiontothehangingeffect,thedirectivityeffectshouldalsobeconsidered.
简介:Inordertodeterminethedegreeofreturning-to-zerooftemperaturesofdeformedcalcite,aseriesofrock-breakingexperimentsweredesignedtotestcalcite-richlimestonesamplesunderfixedconfiningpressuresanddifferenttemperatures.Theconsolidateddeformedsamplesintheirinitialstatewereobservedunderamicroscopeandthemicroscopicindicatorsindifferentzero-returningstateswereputforward,thusprovidingamicroscopicfoundationforevaluationofreliabilityofdatingvaluesofdeformationincalcite.Atlast,thecorrectionofdatingvaluesofdeformationforsampleswhosetemperaturehasnotyetreturnedtozeroisdiscussed.
简介:ThemodeserialsoftheEarth'sfreeoscillationprovidesomeimportantinformationontheEarth'sdeepstructureandsuperconductinggravimeters(SG)caninvestigatethephenomenaoftheEarth'sfreeoscillationswithhighaccuracy.ThegreatSumatra-AndamanearthquakefullyexcitedtheEarth'sfreeoscillationsandthesesignalswereperfectlyrecordedbyfivesuperconductinggravimetersintheglobe.Afterthepre-treatmentandspectralanalysisontheSGobservationdata,weobtainedtheexperimentedmodeserialsoftheEarth'sfreeoscillationsconsistingof147modeswithGGPstationdata.TheseobservedmodeswerethemselvessomenewimportantdataforthestudyoftheEarth'sdeepstructure.Onthebasisofthediscussionsonsomecheckedinner-core-sensitivemodes,wedistinguishedthreelayersfromtheinnercore,andtheboundaryoftheupperlayerwascompatiblewiththeformerlyknowntransitionzoneintheinnercorebasedonseismicbodywavesandsupportedthattherewerethehemisphericalvariationandverylowershearvelocityzoneinthelowerinnercore.
简介:TheHori’sinversemethodbasedonspectraldecompositionwasappliedtoestimatecoseismicslipdistributionontheruptureplaneofthe14November2001MS8.1KunlunearthquakebasedonGPSsurveyresults.TheinversionresultshowsthatthesixslidingmodelscanbeconstrainedbythecoseismicGPSdata.Theestablishedslipsmainlyconcentratedalongtheeasternsegmentofthefaultrupture,andthemaximummagnitudeisabout7m.Slipontheeasternsegmentofthefaultrupturerepresentsaspurelyleft-lateralstrike-slip.Sliponthewesternsegmentoftheseismicrupturerepresentsasmainlydip-slipwiththemaximumdip-slipabout1m.Totalpredictedscalarseismicmomentis5.196×1020N?m.Ourresultsconstrainedbygeodeticdataareconsistentwithseismologicalresults.
简介:ThisstudyproposesaGreen’sfunction,anessentialrepresentationofwater-saturatedgroundundermovingexcitation,tosimulategroundbornevibrationfromtrains.First,generalsolutionstothegoverningequationsofporoelasticmediumarederivedbymeansofintegraltransform.Secondly,thetransmissionandreflectionmatrixapproachisusedtoformulatetherelationshipbetweendisplacementandstressofthestratifiedground,whichresultsinthematrixoftheGreen’sfunction.ThentheGreen’sfunctioniscombinedintoatrain-track-groundmodel,andisverifiedbytypicalexamplesandafieldtest.Additionalsimulationsshowthatthecomputedgroundvibrationattenuatesfasterintheimmediatevicinityofthetrackthaninthesurroundingarea.Thewavelengthofwheel-railunevennesshasanotableeffectoncomputeddisplacementandporepressure.Thevariationofvibrationintensitywiththedepthofgroundissignificantlyinfluencedbythelayeringofthestratasoil.WhenthetrainspeedisequaltothevelocityoftheRayleighwave,theMachconeappearsinthesimulatedwavefield.TheproposedGreen’sfunctionisanappropriaterepresentationforalayeredgroundwithshallowgroundwatertable,andwillbehelpfultounderstandthedynamicresponsesofthegroundtocomplicatedmovingexcitation.
简介:TemporalchangesinsiteeffectsareobtainedusingtheHVSR(horizontal-to-verticalspectralratio)methodandstrongmotionrecordsaftertheMw7.6Chi-Chiearthquake,Taiwan.Seismicdatarecordedbetween1995and2010areused,comprising3,708datafrom15stationsadjacenttotheChelungpufault.Temporalfluctuationsaredeterminedbyanalyzingthesiteeffectvariationusingatime–frequencyvariation(TFV)diagrambasedontheseseismicdata.Stationsadjacenttothefaultshowsignificantdisturbancesintheresonancefrequencyat16–26Hz.StationTCU129showsa40%dropinfundamentalfrequencyafterthemainshock,andagradualreturntotheoriginalstateovernineyears.Forstationslocatedfartherfromthefaultzone,suddenchangesintectonicstressplayadominantroleintemporalchangestotheHVSR.Animpactanalysisofthedirectionalfactorconfirmsourfindingthattheproximityofthefaulttoseismicstationshasthemostinfluenceondata.
简介:正Thethesisofthepaper,whichistheobjectofthisDiscussion,isthattheconsiderabledamagesufferedbytheBasilica,aftertheearthquakeofL'Aquilain2009,wastheexclusiveresultoftheinterventionofseismicimprovementofthenaves,madein2000;such
简介:Alargeearthquake(MW=7.6)occurredinJiji(Chi-Chi),Taiwan,ChinaonSeptember20,1999,andwasfollowedbymanymoderate-sizeshocksinthefollowingdays.TwoofthelargestaftershockswiththemagnitudesofMW=6.1andMW=6.2,respectively,wereusedasempiricalGreen(sfunctions(EGFs)toobtainthesourcetimefunctions(STFs)ofthemainshockfromlong-periodwaveformdataoftheGlobalDigitalSeismographNetwork(GDSN)includingIRIS,GEOSCOPEandCDSN.FortheMW=6.1aftershockofSeptember22,therewere97pairsofphasesclearenoughfrom78recordingsof26stations;fortheMW=6.2aftershockofSeptember25,therewere81pairsofphasesclearenoughfrom72recordingsof24stations.Foreachstation,2typesofSTFswereretrieved,whicharecalledP-STFandS-STFduetobeingfromPandSphases,respectively.Totally,178STFindividualswereobtainedforsource-processanalysisofthemainshock.Itwasnoticedthat,ingeneral,STFsfrommostofthestationshadsimilaritiesexceptthatthoseinspecialazimuthslookeddifferentoroddduetothemechanismdifferencebetweenthemainshockandtheaftershocks;andindetail,theshapesoftheSTFsvariedwithazimuth.BothofthemreflectedthestabilityandreliabilityoftheretrievedSTFs.ThecomprehensiveanalysisofthoseSTFssuggestedthatthiseventconsistedoftwosub-events,thetotaldurationtimewasabout26s,andontheaverage,thesecondeventwasabout7slaterthanthefirstone,andthemoment-rateamplitudeofthefirsteventwasabout15%largerthanthatofthesecondone.
简介:正Theauthorsthankthediscusserforhisinterestandcarefulreviewofthepaperandhisvaluablecomments.Theyalsowelcomethisdiscussion,becauseitgivestheauthorstheopportunitytoclarifyseveralpointswhichwerenotexplainedinsufficientdetailinthepaper,due
简介:Basedonwaveformdata,severalmethodstodeterminefocalmechanismsofsmallearthquakesweredevelopedsince1980.Kisslinger(1980)andJulian,Foulger(1996)proposedanapproachtodeterminesolutionbyusingamplituderatioofPandSwave.Schwartz(1995)devisedamethodtodeterminesolutionsbytheuseofpolaritydataandamplitudesofseismogramenvelopes.Amplitudesofshortperiodseismicwavespropagatinginaninhomogene-ousmediumaresensitivetothevariationinvelocityandQstructure.Nakamura,etal(1999)tookmediuminhomo-geneityintoaccountindeterminingfocalmechanismsofsmallearthquakesusingwaveformdata.Ifthelocationsofsmallearthquakesareconcentratedinasmallregion,wecanassumethattheraypathsfromtheeventstoagivenstationarealmostthesame.SoPandSwaveattenuationsareindependentofeventlocations.Inthiscaseitiscon-venienttodeterminefocalmechanismsoftheseeventsbyusingshortperiodPandSwavedataj.Focalmechanismsolutionsofsmallearthquakesin5regions,i.e.,Rongchang,Mabian-Muchuan,Ya¢an,BaoxingandMianzhu,whicharecoveredbytheChengduTelemeteredNetwork,areobtainedbyanalyzingthePpolarityandshortbodywaveamplitudedatarecordedinthenetworksince1992.AccordingtothemethodproposedbyGephartandForsyth(1984),basedonwelldeterminedfocalmechanismsolutionsin15sub-zonesofSichuanandYunnanarea,threeprincipalstresstensorss1,s2,ands3,insteadofaveragesofP,B,andTaxisofthesolutions,aredeterminedtorepresenttheregionalstressfielddistribution.