简介：1SURVEYOFGLOBALSEISMICITYIN2013Atotalof23strongearthquakeswithMS≥7.0occurredin2013throughouttheworldaccordingtotheChinaSeismicNetwork(Table1).ThestrongestearthquakewasintheSeaofOkhotsk,measuringMS8.2onMay24(Fig.1).Earthquakesoccurredmainlyinthewesternpartofthecircum-Pacificseismicbelt.Comparedwiththeseismicityin2012,thefrequencyincreasedsignificantlyandtheenergyreleaseofearthquakeswasobviouslylow.FeaturesofglobalseismicityofMS≥7.0areasfollows:

简介：Usingthedouble-differencerelocationalgorithm,werelocatedthe20April2013Lushan,Sichuan,earthquake(MS7.0),andits4,567aftershocksrecordedduringtheperiodbetween20AprilandMay3,2013.Ourresultsshowedthatmostaftershocksarerelocatedbetween10and20kmdepths,butsomelargeaftershockswererelocatedaround30kmdepthandsmalleventsextendedupwardnearthesurface.Verticalcrosssectionsillustrateashovel-shapedfaultplanewithavariabledipanglefromthesouthwesttonortheastalongthefault.Furthermore,thedipangleofthefaultplaneissmalleraroundthemainshockthanthatinthesurroundingareasalongthefault.Theseresultssuggestthatitmaybeeasytogeneratethestrongearthquakeintheplacehavingasmalldipangleofthefault,whichissomewhatsimilartothegenesisofthe2008Wenchuanearthquake.TheLushanmainshockisunderlainbytheseismicallyanomalouslayerswithlow-VP,low-VS,andhigh-Poisson’sratioanomalies,possiblysuggestingthatthefluid-filledfracturedrockmatricesmightsignificantlyreducetheeffectivenormalstressonthefaultplanetobringthebrittlefailure.TheseismicgapbetweenLushanandWenchuanaftershocksissuspectedtobevulnerabletofutureseismicrisksatgreaterdepths,ifany.

简介：Aseismicarrayoftwentyfourseismometers(Qiaojiaarray)operatedbytheInstituteofGeophysics,ChinaEarthquakeAdministrationwassituatedalongtheZemuhefaultandthenorthendofXiaojiangfault,whichisapartoftheeastboundaryoftheChuan-Dian(Sichuan-Yunnan)rhombuscrustalmass.TheQiaojiaarraystartedoperationattheendofFebruary,2012.SincethentheApril20,2013LushanMS7.0earthquakeandtheAugust3,2014LudianMS6.5earthquakehaveoccurredinthevicinityoftheQiaojiaarray.TheearthquakecataloguerecordedbytheQiaojiaarraysinceMarch,2012isusedinthisstudy.ThetemporalvariationoftheearthquakecountbeforetheLushaneventandtheLudianeventisanalyzed.Theresultsareasfollows:①AverycleargraduallyincreasingvariationofthecountofM≥2.0earthquakeswithintheregion,whereallearthquakesrecordedbytheQiaojiaarraycoveragecanbefoundbeforetheLushaneventandtheLudianevent,andtheincreasingrangeanddurationofthecountbeforetheLudianeventarebothlargerthanthosebeforetheLushanevent.②IntheregioncoveredbytheQiaojiaarray,forearthquakeswithdepthh≤10kmarisingprocessofthecountwasmanifestedbeforebothevents,alongwithanearlysamedurationofaboutfiveandahalfmonths,andforearthquakeswithdepthsh>10kmarising-droppingprocessofthecountwasmanifestbeforetheLushanevent,beforewhichtherising-droppingprocessappearedagain.Thevariationofthecountforearthquakeswithdepthh≤10kmisthereverseofthatforearthquakeswithdepthh>10km.③WithinandneartheregioncoveredbytheQiaojiaarray,thevariationofthecountmanifestsarisingprocessforearthquakeswithdepthh≤10kmorh>10kmbeforetheLushaneventandonlyforearthquakeswithdepthh≤10kmbeforetheLudianevent.Thevariationofthecountmanifestsaweakeningprocessforearthquakeswithdepthh>10kmbeforetheLushanevent.Itisshownfromtheaboveresultsthattheseismicitywit

简介：传统的傅里叶变换因缺乏信号局域性的信息,无法对地震波等非平稳信号进行全面描述,时频分析通常是分析非平稳信号较好的工具.本文利用大柴旦地震台记录到的2013年6月5日青海海西5.0级地震波形,采用赵-阿特拉斯-马克时频分布（ZAM）分别研究了该地震P波、S波段的时间-频率特征.研究结果很好地解释了地震波的非平稳性,较全面地展示了地震波的衰减特征.

简介：Thedensebroadbandseismicnetworkprovidesmorehigh-qualitywaveformthatishelpfultoimproveconstraintfocaldepthofshallowearthquake.Manyshallowearthquakesoccurringinsedimentwereregardedasinducedevents.InSichuanbasin,gasindustryandsaltminingaredependentonfluidinjectiontechniquethattriggersmicroseismicity.WeadoptedwaveforminversionmethodwithregionalrecordstoobtainfocalmechanismofanMs4.8earthquakeatChangning.TheresultsuggestedthattheChangningearthquakeoccurredataESEthrustfault,anditsfocaldepthwasabout3km.ThedepthphasesincludingteleseismicpPphaseandregionalsPLphaseshowsthatthefocaldepthisabout2km.Thestrong,shortperiodsurfacewavesuggeststhatthiseventisaveryshallowearthquake.TheamplituderatiobetweenRayleighwaveanddirectSwavewasalsousedtoestimatethesourcedepthofthemainshock.Thefocaldepth(2–4km)isfarlessthanthedepthofthesedimentarylayerthickness(6–8km)inepicentralregion.Itisclosetothedepthoffluidinjectionofsaltmining,whichmayimplythatthiseventwastriggeredbytheindustrialactivity.

简介：2013年8月12日在西藏自治区左贡与芒康交界发生6.1级地震,该地震宏观震中位于左贡县田妥镇嘎益村-仁果乡吞永村一带,最大烈度Ⅷ度,但不构成Ⅷ度区.根据现场工作队所收集的资料,分析了震区各类房屋建筑的震害特征及其破坏原因,并根据此次地震对该地区房屋所造成的破坏程度提出了防震减灾研究建议,并强调了此类民居需要加强抗震设计.

简介：BasedonthewaveformdataobservedbytheregionalseismicnetworkofGansuProvince,wecalculatedtheapparentstressof422earthquakeswithM_L≥2.0occurringinthesurroundingareaoftheMinxianearthquakefromJanuary2010toJuly2014andobtainedthetemporalandspatialvariationofapparentstressbeforeandaftertheMinxianearthquake.Resultsshowthat(1)thehighvalueofapparentstressofearthquakeswithM_L≥4.0wasconcentratedintheepicenterareabeforetheMinxianearthquakewhilethatofearthquakeswithM_L<4.0wasnot;(2)ApparentstressaroundtheepicenterareashowedanobviousincreasingprocessbeforetheMinxianearthquakeandtheincreasingprocesshascontinuedafterthemainshock,whichmeansthatthisstudyareaisstillinthedangerofstrongearthquakes.

简介：OnJuly22,2013,theMinxian-ZhangxianM_S6.6earthquakeoccurredontheeastsegmentofLintan-Dangchangfault.TheanalysisofdigitalelevationandremotesensingimagingshowsthattheeastsegmentofLintan-Dangchangfaultisstillactiveandthemainthrustfeatureofthefaultswitchestoleftlateralslip.Withthefieldresearchofintensityanddamage,severalabnormalareasofdegreeⅧspreadintheisoseismallineofdegreeⅦandsomeabnormalareasofdegreeⅦspreadintheisoseismallineofdegreeⅥ.Theseabnormalareasaredistributedalongthehangingwallofthefaultinawidthof2km.TheanalysisbasedontheremotesensinganddigitalelevationmodelshowsthatthesegmentoftheLintan-DangchangfaultsouthofMinxianmainlyslipsinleftliteral.Thefaultmovementmadethesoilsoftinthefaultzone.Theearthquakemotionpropagatedalongthefaultzone.Thereforethestrongearthquakemotioncausedfoundationfailureinthesoftsoilalongthefaultzoneandtheabnormalintenseareasofdisasterformed.