简介：ShanxiGrabenisinthemiddlepartoftheNorthChinaCraton,fromsouthtonorth.WiththeteleseismicdatarecordedbyRegionalSeismographNetworksandthetemporaryZBnet-WSeismicArrayaroundeastpartofShanxiGraben,wemeasuredthecrustalthicknessandvP/vSratiobeneatheachstationusingtheH-jstackofreceiverfunctions.Theobservedcrustalthicknessshowsobviouslateralvariation,increasinggraduallyfromeasttowestintheShanxiGraben.BeneaththeShanxiGrabenthecrustisrelativelythickerthanbothsidesofthesouthandthenorth.Inaddition,thevP/vSratiointhenorthofstudyzoneishigherthanthatinthesouth.ThehighestvP/vSratioexistsinthecrustoftheXindingbasinandtheDatongbasin.Ourstudyalsosuggeststhathighvelocityratiomightresultfromthestrongactivitiesofthemagmationandvolcanism.

简介：ThegeologicalstructureiscomplexintheHohhot-Baotouarea.SeveralearthquakeswithMS≥6.0haveoccurredintheareainhistory.ThisarticleselectedtheHohhot-Baotouareaasthestudyregionanddivideditinto2sub-regions,eachwithaspatialscopeof3°×2°,accordingtothespatialdistributionofML≥1.0earthquakesoccurringbetweenJanuary2001andApril2010,andthelayoutoftheseismicnetworkinthestudyregion.Averagevelocityratiosofrespectivesub-regionswerecalculated,andcomparativeanalysiswasmadeontheirtemporalandspatialvariations.Resultsshowthatthereareslightdifferencesbetweensub-regionsinthevariationamplitudeofaveragevelocityratiocurvesovertime,whichmostlyremainsbetween2.5%to2.584%.IntheHohhotarea,theaveragevelocityratiois1.722,significantlylowerthantheaveragevelocityratioof1.733intheBaotouarea.WepreliminarilyconcludedthatthiswasrelatedtothedistributionoffaultstructuresandpropertiesofundergroundmediaintheHohhotarea.

简介：总结提出了提高黔江地震台VS型垂直摆观测资料分析预报可靠性的工作方法与步骤,旨在为今后地震前及时发现前兆异常提供参考。运用调和分析法、差分法分析了2016年至2017年观测数据,认为武隆5.0级地震前出现了地震前兆异常。同时,认为对黔江地震台VS型垂直摆原始观测资料按30天的步长进行计算效果较为理想。

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简介：Mesoscaleensembleisanencouragingtechnologyforimprovingtheaccuracyofheavyrainfallpredictions.Occurrencesofheavyrainfallarecloselyrelatedtoconvectiveinstabilityandtopography.Inmid-latitudes,perturbedinitialfieldsformedium-rangeweatherforecastsareoftenconfiguredtofocusonthebaroclinicinstabilityratherthantheconvectiveinstability.Thus,alternativeapproachestogenerateinitialperturbationsneedtobedevelopedtoaccommodatetheuncertaintyoftheconvectiveinstability.Inthispaper,aninitialconditionperturbationapproachtomesoscaleheavyrainfallensembleprediction,namedasDifferentPhysicsModeMethod(DPMM),ispresentedindetail.BasedonthePSU/NCARmesoscalemodelMM5,anensemblepredictionexperimentonatypicalheavyrainfalleventinSouthChinaiscarriedoutbyusingtheDPMM,andthestructureoftheinitialconditionperturbationisanalyzed.Further,theDPMMensemblepredictioniscomparedwithamulti-physicsensembleprediction,andtheresultsshowthattheinitialperturbationfieldsfromtheDPMMhaveareasonablemesoscaiecirculationstructureandcouldreflectthepredictionuncertaintyinthesensitiveregionsofconvectiveinstability.AnevaluationoftheDPMMinitialconditionperturbationindicatesthattheDPMMmethodproducesbetterensemblemembersthanthemulti-physicsperturbationmethod,andcansignificantlyimprovetheprecipitationforecastthanthecontrolnon-ensemblerun.

简介：BasedonarrivaltimedataofseismicphasesofML≥2.0earthquakesmeasuredatShanxiDigitalSeismicNetworkfortheperiodfromJanuary2001toOctober2014,V_P/V_SintheShanxiregioniscalculatedusingtheWadatisinglestationandmulti-earthquakemethod,andaninvestigationisconductedintothevariationbehaviorofV_P/V_SintheShanxiregionbeforeandafterthethreeearthquakesofMS≥4.5in2010.OurstudyfindsthatabnormalV_P/V_Sappearedearlieratdistantstationsbeforeallofthethreeearthquakes,whichisatthetimerangefrom6monthsto1yearbeforetheearthquakes,andlateratnearstations,atthetimerange10daysto2monthsbeforeearthquakes.Therefore,itspossibletonarrowdownthescopeofthelocationinearthquakepredictionfromthedistantandnearstationdata.ThecalculationsofDongshanseismicstationindicatethatthesizeoftheresidualoftheorigintimehasimpactonthedetailofV_P/V_Svariation,thus,appropriatethresholdsshouldfirstlybesetfortheresidualsoforigintimeateachseismicstationinpracticalapplication,toensurescientificandsteadyV_P/V_Scalculations.

简介：本文收集了733个四川地区的实测钻孔数据,从中筛选出深度大于30m的268个钻孔剖面资料.分别获得了10m、15m、20m、25m和28m不同深度处的平均剪切波速（Vs）（d）与（Vs）（30）的对数线性相关关系.同时还与Boore（2004）的结果做了对比分析,比较了采用常数外推法和对数线性外推法得到的不同深度处剪切波速的残差分布.结果表明,不同深度处剪切波速（Vs）（d）与（Vs）（30）的对数相关关系可能具有一定的区域性特征,本文得到的对数关系更适合四川地区.对数线性外推法与常数外推法相比,前者的系统偏差更小;随着深度的增加,两种方法的外推误差均逐渐减小,但常数外推法普遍低估了（Vs）（30）值;当深度较浅时,低估的情况更为明显.本文的研究结果为利用大量的不足30m的钻孔资料估计（Vs）（30）值提供了参考.

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简介：本文提出了一种新的反演方法:通过采用纵、横波走时数据对(从相同的震源产生的P和S波被同一台站记录)来联合反演纵波速度(Vp)和纵、横波速度比(Vp/Vs),然后单独反演横波速度Vs,在反演过程中同时对地震参数进行定位。该方法不需要假设P和S波的射线路径一致,它是沿着P和S波射线路径计算相对慢度扰动值。该方法直接把Vp/Vs作为一个模型参数,由此能获得比采用从独立反演获得的Vp和Vs计算出Vp/Vs的方法更精确的速度比值。该新方法被应用到反演日本东北地区的壳幔速度及波速比结构的研究中,获得了较好的效果。反演结果表明,在日本东北地区,太平洋俯冲板块为一高Vp,高Vs和低Vp/Vs异常区,而在活火山下方的浅部地幔楔以及背弧深部地区为低Vp,低VS和高Vp/VS异常。虽然这些特征在前人的研究中已经报道过,但与前人的研究结果相比,本次研究所获得的Vp/Vs的空间分布具有较小的分散性,同时,它的分布特征能较好的与地震波速度结构相吻合。

简介：Anew3Dvelocitymodelofthecrustanduppermantleinthesoutheastern(SE)marginoftheTibetanplateauwasobtainedbyjointinversionofbody-andsurface-wavedata.Forthebody-wavedata,weused7190eventsrecordedby102stationsintheSEmarginoftheTibetanplateau.Thesurface-wavedataconsistofRayleighwavephasevelocitydispersioncurvesobtainedfromambientnoisecross-correlationanalysisrecordedbyadensearrayintheSEmarginoftheTibetanplateau.ThejointinversionclearlyimprovesthevSmodelbecauseitisconstrainedbybothdatatypes.Theresultsshowthatataround10kmdepththerearetwolow-velocityanomaliesembeddedwithinthreehigh-velocitybodiesalongtheLongmenshanfaultsystem.Thesehigh-velocitybodiescorrespondwellwiththePrecambrianmassifs,andthetwolocatedtothenortheastof2013MS7.0Lushanearthquakeareassociatedwithhighfaultslipareasduringthe2008Wenchuanearthquake.Theaftershockgapbetween2013Lushanearthquakeand2008Wenchuanearthquakeisassociatedwithlow-velocityanomalies,whichalsoactsasabarrierzoneforrupturesoftwoearthquakes.Generallylargeearthquakes(M≥5)intheregionoccurringfrom2008to2015arelocatedaroundthehigh-velocityzones,indicatingthattheymayactasasperitiesfortheselargeearthquakes.Jointinversionresultsalsoclearlyshowthatthereexistlow-velocityorweakzonesinthemid-lowercrust,whicharenotevenlydistributedbeneaththeSEmarginofTibetanplateau.