简介:公元1590年7月,在甘肃临洮附近有破坏性历史地震记载“……坏城廓庐舍,压死人畜无算”。同月,青海东部的冰沟城(今乐都县东北)也因地震而城崩。在过去出版的地震目录中,均按两次地震列出,分别称为甘肃临洮5Y2级地震,震中烈度Ⅶ度:青海乐都5级地震,震中烈度Ⅵ度。根据史料考证和现场调查结果,综合分析认为,上述两次地震很有可能为同一次地震,其震中位于甘肃永靖东南的马衔山区,震中烈度达Ⅷ一Ⅸ度,震级6V2级左右,其发震构造很可能为兰州马衔山北缘断裂带的中西段。
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:TheseismicwaveformoftheYutianMS7.3earthquake,XinjiangonFebruary12,2014wasrecordedclearlyandcompletelybytheDigitalSeismicNetworksofXinjiang,Qinghai,Tibet,andXinjiangHotanarray,sothemethodofjointlocationbyregionalseismicnetworkandseismicarraycanbeusedtoaccuratelydeterminetheearthquakesourcelocation.Thefollowingtechnologieswereusedintheprocessoflocation:(1)WeselectedseismicstationsequallylocatedaroundtheepicenteroftheMS7.3earthquakewithanaverageintervalofabout15degreesintheinitiallocation.(2)TherecordingwaveformsofYutianseismicstationwererotatedtotheradialandtangentialdirectionstopreciselyobtainthearrivaltimeofS-wavestodeterminetheepicentraldistance.(3)Thevelocitymodelwasusedinthedeterminationoflocationoftheepicenter,basedonthehistoricalrecordsofearthquakesintheareawithinaradiusof1.0°fromthesourceasthecenter,andthevelocitymodelisobtainedafterre-fittingandcalibration.(4)BasedonthewaveformrecordsoftheHotanseismicarray,themethodofwaveformbeamingwasusedtodeterminetheazimuthsandperformthecorrectionoftheepicenterlocationwiththeseazimuths.(5)Thedeterministicmethodwasusedtomeasurethesourcedepth.Finally,itisconcludedthattheYutianMS7.3mainshockhypocenterlocationis36.197°N,82.467°E,focaldepth12kmandoriginaltime17:19:48.2p.m.February12,2014.
简介:ThispapercalculatesthestaticCoulombstresschangesgeneratedbyfourearthquakesintheYutianareaduring2008~2014separately,thendiscussesthetriggeringinfluence,theiraccumulatedCoulombstresschangesandtheirinfluenceonnearbyfaults.TheresultsindicatethattheMS5.5earthquakein2011andtheM_S7.3earthquakein2014arebothintheregionswheretheCoulombstresschangeispositive,thestresschangesare0.004MPaand0.021MPa,respectively,meaningtheyaretriggeredbypriorearthquakes.TheMS6.2earthquakein2012occurredintheplacewhereCoulombstresschangewasnegative,soitispostponedbythepriorearthquakes.TheimageofCoulombstresschangesoftheMS7.3earthquakein2014isinaccordwithaftershocks(ML≥3.0)distribution,butsomeregionsonthefaultwheretheCoulombstresschangeispositivehavefewaftershocks,andstrongaftershocksmayoccuratthesedistrictsinfuture.Inaddition,thispapercalculatestheCoulombstresschangeonnearbyfaults,andfindsthattheCoulombstresschangesofdifferentelementsintheGGCfaultareverydifferent,andmustreceivestrongtriggered-influence,thoughtheresultmaybeinfluencedbytheinputfinitefaultmodel,sothereisstillalargeearthquake-risk.TheGGN,PLC,PLWandLBWfaultswerealsotriggeredbythefourearthquakesoccurringbetween2008~2014.TheirmaximumCoulombstresschangesallexceed0.002MPa,sotheyalsohaveastrongearthquakehazard.
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.
简介:TheYutianearthquakewithM_S7.3happenedonFebruary12,2014.Theprecursormonitoringabilityisweakinthatarea.Wefoundtendencyanomaliesandmiddle-andshort-termanomaliesfrommetalpendulumtiltmeasurementsinHotanseismicstationbeforetheearthquake.AndwealsocomparedtheanomalieswiththatoftheM_S7.3YutianearthquakeonMarch21,2008.Thetendencyanomaliesmeasuredbythemetalpendulumtiltmeterappearedsince2012astiltingeastward.Whilethemiddle-andshort-termanomalieswerecharacterizedbyacceleration,pauseandrapidchangeoftiltrateintwodirections.Thetendencyanomaliesofmetalpendulumtiltrecordsarethesamebeforethetwoearthquakes.Theybothhappenedintheeastdirection.However,therearedifferencesinduration,characteristicandearthquakeintervalsforthemiddle-andshort-termanomalies.
简介:AnearthquakewithM7.1occurredinYushu,QinghaiProvince,China,at07:49a.m.onApril14,2010,accordingtotheChineseSeismicStationNetwork.Thesequenceisafore-mainafter-shocktypesequence.AforeshockwithM4.7occurred2hoursand11minutesbeforethemainshock.Therewere12foreshocksand2385aftershocksuntilJune31,2010.Inwhich,thereare21aftershocksbetweenM3.0andM3.
简介:枚举的算法被介绍了进ASR模型的恰当的过程。与M6基于21大地震的详细学习。8在中国大陆,在大地震前的地震紧张版本的统计特征被总结了。在团中,紧张版本模型能被划分成五种类型。第一是DA模型,紧张版本在更宽广的区域在加速并且在震中附近在小区域速度。约38%地震样品具有这种类型。第二是AD模型,紧张版本在更宽广的区域在速度并且与占据ratioof在震中附近在更小的区域加速约19%。第三是ASR,仅仅加速的紧张版本能在被观察。这个模型的盒子等于大约14%。第四是数据设置就绪,仅仅速度的紧张版本能在被检查,等于大约24%。仅仅有第五种类型(LSR)的一件地震样品,它显示出一个线性紧张版本。在持续时间有36年差别预先震惊在加速并且速度的模型之间的序列。在大地震一般来说是一个典型特征以前,这对小地震的增加的seismicity的一个背景意味着那地震静止。为DA模型,分别地,为稳定的加速并且速度的紧张版本的批评区域的平均尺寸关于到400km和100km的260km到200km3~5次,1~2预定大小7的地震的破裂尺寸。0。广告模型是DA模型的反面。模型参数,m价值,好稳定性。ASR的比率关于为加速地震紧张版本现象的一样,不管紧张版本模型是什么,或紧张版本数量怎么大。关于速度地震紧张版本现象,DA模型有最特殊的速度紧张版本特征并且是地震紧张版本的典型特征,我。e。“速度在里面加速外面地震紧张模型”。
简介:Wesuccessfullyemployanautomaticcentroidmomenttensor(CMT)inversionsystemtoinfertheCMTsolutionsoftheFebruary12,2014MS7.3Yutian,Xinjiangearthquakeusingnear-fieldseismicwaveforms(4°<△<12°)observedbythevirtualChinaseismicnetworks,whichhavebeenrecentlysetup.Theresultsindicatethatthiseventoccurredonaruptureplane(strike243°,dip70°,andrake-18°),showingleft-lateralstrike-slipfaultingwithaminornormal-faultingcomponent.Thecentroidinthehorizontaldirectionislocatednearly13kmeastoftheepicenter(36.123°N,82.499°E),andthebest-fittingcentroiddepthisaround10km.Thetotalscalarmoment,M0,isretrievedwithanaveragevalueof3.05×1019N·m,correspondingtomomentmagnitudeMW6.92.Mostoftheenergyisreleasedwithinabout14s.Moreover,wediscussaboutthepotentialapplicationofthissysteminearthquakedisasterdecision.