简介:High-frequencyruptureprocessoftheOct23,2011Van-Merkezearthquakeisimagedbyback-projectionmethodusinghigh-qualityteleseismicPwavedatafromtheUSArray,andprestackKirchhoffmigrationusingPwavedatafromasubarrayofglobalseismicnetworks.Therupturemodelwithtwoasperitiesisconfirmedbyprevioustwomethods.Inlow-frequencyimaging,alargeasperityderivedfromthemigrationmethodcorrespondstothesecondonefromthehigh-frequencyPwaves.Theconsistencyofthelocationsofasperitiesfromdatasetswithdifferentfrequencybandsindicatesthatthereispossibleinsignificanceofthefrequency-dependentfeaturefortheearthquake.Theresultantimagesillustratethespatialandtemporalevolutionoftherupture,whichmainlypropagatedWSWoveralengthof33kmduringthefirst18s,accompanyingwithburstsoftwoasperitiesat3and11–13s.TherupturedirectionisconfirmedbytheSwavecornerfrequencyvariationsofstronggroundaccelerations.Therupturefrontsaremainlylocatedattheupdipofthecausativefault.BasedonpolaritiesofthePwaveformsandfocalmechanismsofthemainshockandaftershocks,thefailureofthesetwoasperitiesisdeterminedtohaveoccurredonareversefaultwithadipangleof47°.Hence,therupturepatternofthe2011Van-Merkezearthquakewasdominatedbyaunilateralrupturetowardthewestsouthwestdirection.
简介:一、地震基本参数表1 地震基本参数表发震时间年月日时分秒震 中 位 置微 观宏 观东经北纬东经北纬参考地名震级(ML)震源深度(Km)震中烈度 地震类型 1978112305492591184°239°漳浦海外41Ⅴ主震型 注:震中位于海中,表中烈度为估计值。二、烈度分布本次地震震级不高,震中又位于海中,未造成任何破坏,但有感面积大。地震后,在厦门及漳州两地市区近海岸带的部分县城,乡镇所在地共24个点,走访600多人进行座谈形式的调查。调查均位于Ⅳ度烈度区内。地震时,室内大多数人有感觉,室外活动的人有感的较少,少数人从梦中惊醒。人们普遍感到床铺等在摇摆,听到玻璃窗在轻微作响。图6-1 1998
简介:AM_L3.8earthquakeoccurredonFebruary23,2014inRongchangCounty,whichislocatedatthesouthernedgeoftheSichuanBasinintheborderareabetweenSichuanandChongqing.ThispaperpresentsresultsoffocalmechanismsolutionofthisearthquakeusingtheCAP(cutandpaste)methodbasedonbroadbandseismogramsrecordedbyregionalseismicstations.OurresultsshowthatthemomentmagnitudeisM_W3.09andfocaldepthis3km.ThehypocenterofthisearthquakeislocatedclosetoaburiedfaultintheLuoguangshananticline.Oilprospectinganddeepdrillingdataindicatethatthisburiedfaultisathrustfault,strikingSW230°,dippingNW45°,and1.7kmdeep.Therearesomeinjectionwellswithintheanticline,andsignificantinjection-inducedearthquakeswereobservedduringtheperiodsofinjectionofwastewaterintothedeepformationsthroughthosewells.ThebestdoublecouplesolutionoftheM_L3.8earthquakeis247°,48°and104°forstrike,dipandrate,respectively,foronenodalplane(and46°,44°and74°foranothernodalplane),whichisinagreementwiththegeometryoftheburiedfault.Therefore,weconcludethattheM_L3.8Rongchangearthquakeispossiblytheresultoffaultingalongtheburiedreversefaultinducedbywaterinjectionunderthecompressivestressregimeinthearea.