简介:Adetailthree-dimensionalPwavevelocitystructureofBeijing,TianjinandTangshanarea(BTTarea)wasdeterminedbyinvertinglocalearthquakedata.Intotal16048Pwavefirstarrivaltimesfrom16048shallowandmid-depthcrustalearthquakes,whichoccurredinandaroundtheBTTareafrom1992to1999wereused.ThefirstarrivaltimesarerecordedbyNorthernChinaUnitedTelemetrySeismicNetworkandYanqing-HuailaiDigitalSeismicNetwork.Hypocentralparametersof1132earthquakeswithmagnitudeML=1.7~6.2andthethree-dimensionalPwavevelocitystructurewereobtainedsimultaneously.TheinversionresultrevealsthecomplicatedlateralheterogeneityofPwavevelocitystructurearoundBTTarea.Thetomographicimagesobtainedarealsofoundtoexplainotherseismologicalobservationswell.
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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.
简介:AnanalyticalsolutionforscatteringofplanePwavesbyasemi-cylindricalhillwasderivedbyusingthewavefunctionexpansionmethod,andconvergenceofthesolutionandaccuracyoftruncationwereverified.Theeffectofincidentfrequencyandincidentangleonthesurfacemotionofthehillwasdiscussed,anditwasshownthatahillgreatlyamplifiesincidentplanePwaves,andmaximumhorizontaldisplacementamplitudesappearmostlyattheinclinedincidenceofwaves,whicharelocatedatthehalf-space;andmaximumverticaldisplacementamplitudesemergemostlyattheverticalincidenceofwaves,whicharesituatedatthehill.
简介:Thispaperreviewstherecentprogressinthestudiesofexperimentalrockmechanicsandtectonophysicsconcern-ingseismologyandphysicsoftheEarth'sinteriorinChina.Theprogressispresentedinthefollowingaspects:a)Alotofresultsofexperimentandnumericalsimulationenrichourknowledgeofthebrittlefracturingprocessundertheconditionwithheterogeneityinmaterialandstructure;b)Somenewresultsonfrictionalbehaviorofnon-homogeneousfaultsrevealthecomplexityoffaultingbehavior;c)Somenewresultsonthebrittle-plastictran-sitionandplasticflowareobtained;especiallytheimportantprogressisobtainedontheologicalpropertiesofrocksinthelowercrustandtheuppermantle;d)Alotofexperimentalresultsareobtainedonrockphysicsathightem-peratureandpressureandhavebeenusedinstudyofmaterialcompositionandstate.TheseresultsprovideusefulinformationforunderstandingthephysicalpropertiesanddeformationmechanismsofmaterialoftheEarth'sinte-riorandearthquakephysics.
简介:本文分析了台湾恒春海外的一次地震的记录波形的P波的主要特征。首先对其首波PN进行分析,结果表明其线性关系较好,计算出的速度值与华南地区近震走时表中所用的地壳模型中的速度值一致。其次对其PN波的续至波进行分析,发现该处的地震其射线穿过台湾岛后的地震记录波形明显与没有穿过台湾岛的不同,即没有穿过台湾岛的地震记录波形中首波震相之后明显存在有另一组震相,而穿过台湾岛后的地震记录波形则没有或不明显。该组震相最明显特征是它与首波的到时差随震中距的加大而减小,据此,作者认为它可能是一组波,即地壳内的双程反射波,表明该处有低速层存在。分析结果表明,台湾海峡南部即福建省的东山海外地区及泉州、漳州、永安地区的下方有一低速层存在。