简介:Inordertodeterminethedegreeofreturning-to-zerooftemperaturesofdeformedcalcite,aseriesofrock-breakingexperimentsweredesignedtotestcalcite-richlimestonesamplesunderfixedconfiningpressuresanddifferenttemperatures.Theconsolidateddeformedsamplesintheirinitialstatewereobservedunderamicroscopeandthemicroscopicindicatorsindifferentzero-returningstateswereputforward,thusprovidingamicroscopicfoundationforevaluationofreliabilityofdatingvaluesofdeformationincalcite.Atlast,thecorrectionofdatingvaluesofdeformationforsampleswhosetemperaturehasnotyetreturnedtozeroisdiscussed.
简介:Inthispaper,basedonGansuDigitalSeismicNetworkdatasince1990,wecalculatedb-valueand⊿b-valueoftheneighborhoodareabeforethe2013Minxian-ZhangxianM_S6.6,earthquake.Theresultsshowthattheearthquakeoccurredatthemarginofthesignificantlylowerb-valueareainsoutheastofGansuandbeforetheearthquaketheneighborhoodareahadanobviouslyabnormal⊿b-value.Fromtheearthquakeandthespatialdistributionoflowb-value,theregionstillhasthepossibilityofgeneratingdangerousstrongearthquakes.
简介:汶川Ms8.0级地震发生在青藏高原东缘著名的龙门山断裂带上,造成了中央断裂和前山断裂共约330kin的地震地表破裂带。初步研究表明,龙门山断裂带上大震复发可能属特征地震模式。结合龙门山断裂带的地震地质情况和汶川地震地表破裂带的基本参数综合分析,本文从地质学、地震学和GPS数据分析三个方面评估了龙门山断裂带的大震复发周期。结果表明,上述三种方法获得的龙门山断裂带Ms8.0级地震的复发间隔分别为:3185a、170(02264a和4310a,平均为3000a左右:Ms7.5级地震的平均复发间隔为1000a左右;Ms7.0级地震的平均复发间隔为500a左右。这些结果与其他学者的研究结果相比,相差不多,基本反映了龙门山断裂带的地震能量水平和累积速度。
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。
简介:针对10种不同坡角的凸起地形,采用基于透射边界的有限元-有限差分计算方法,研究了局部凸起在SV波斜入射时,地震动峰值加速度放大倍数和反应谱谱比随入射角度的变化规律。结果表明:(1)地震波以一定的角度斜入射时,地表大部分观测点的峰值加速度放大倍数大于垂直入射的情况;(2)在计算模型宽高比一定的情况下,最不利入射角度与坡角有一定关系,且地表最不利位置随坡角增大由凸起台地边缘向中心移动;(3)入射角度对凸起地形地震反应谱特性的影响十分显著,不但影响谱比的幅值,也影响谱比曲线的形状,斜入射时各关键节点大部分周期点的谱比值大于垂直入射,入射角度对反应谱中的高频成分影响较为显著,而对长周期成分影响不大。
简介:Complex time-space spreading and focal mechanism of the 1989 Batang earthquake swarm (M_s=6.7)(程万正)(陈天长)Complextime-spacespre...
简介:BasedonthewaveformdataobservedbytheregionalseismicnetworkofGansuProvince,wecalculatedtheapparentstressof422earthquakeswithM_L≥2.0occurringinthesurroundingareaoftheMinxianearthquakefromJanuary2010toJuly2014andobtainedthetemporalandspatialvariationofapparentstressbeforeandaftertheMinxianearthquake.Resultsshowthat(1)thehighvalueofapparentstressofearthquakeswithM_L≥4.0wasconcentratedintheepicenterareabeforetheMinxianearthquakewhilethatofearthquakeswithM_L<4.0wasnot;(2)ApparentstressaroundtheepicenterareashowedanobviousincreasingprocessbeforetheMinxianearthquakeandtheincreasingprocesshascontinuedafterthemainshock,whichmeansthatthisstudyareaisstillinthedangerofstrongearthquakes.
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:IntroductionRegionalseismicitytriggeredbybigearthquakesaswellasattershocksinsourcezonecouldbedetectedduetothehighseismicmonitoringcapabilitytoday(Anderson,etal,1994;Bodin,Gomberg,1994;Caskey,Wesnousky,1997;Deng,Sykes,1996;Hill,etal,1993;King,etal,19...
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:TheregionaltectonicbackgroundandcharacteristicsofactivefaultsoftheYutianMS7.3earthquakeonFebruary12,2014arediscussedinthispaper.AftertheanalysisoftheepicenterareaoftheMS7.3earthquakein2014andthefocalmechanismsoftheformerstrongearthquakesaroundit,theauthorsdeducedthattheseismogenicfaultoftheMS7.3earthquakeistheeastbranchoftheAshikulefault.TheMS7.3earthquakein2014andtheMS7.3earthquakein2008aretwostrongearthquakeeventsonthedifferentsectionsoftheAltunTaghfault,wherethefaultbehaviorchangesfromsinistralsliptonormalfaultingbecauseoftheextensionaltaileffectsinthesouthernendoftheAltunTaghfault.ItisconcludedthatthetwoMS7.3earthquakeshavethesamedynamicsource,andtheMS7.3earthquakein2008promotedtheoccurrenceoftheMS7.3earthquakein2014.Finally,wecalculatetheCoulombstresschangetotheseismogenicfaultoftheMS7.3earthquakein2014fromtheMS7.3earthquakein2008usingthelayeredcrustmodel.TheresultalsoshowsthattheMS7.3earthquakein2008acceleratedtheoccurrenceoftheMS7.3earthquakein2014.