简介:Basedonwaveformdata,severalmethodstodeterminefocalmechanismsofsmallearthquakesweredevelopedsince1980.Kisslinger(1980)andJulian,Foulger(1996)proposedanapproachtodeterminesolutionbyusingamplituderatioofPandSwave.Schwartz(1995)devisedamethodtodeterminesolutionsbytheuseofpolaritydataandamplitudesofseismogramenvelopes.Amplitudesofshortperiodseismicwavespropagatinginaninhomogene-ousmediumaresensitivetothevariationinvelocityandQstructure.Nakamura,etal(1999)tookmediuminhomo-geneityintoaccountindeterminingfocalmechanismsofsmallearthquakesusingwaveformdata.Ifthelocationsofsmallearthquakesareconcentratedinasmallregion,wecanassumethattheraypathsfromtheeventstoagivenstationarealmostthesame.SoPandSwaveattenuationsareindependentofeventlocations.Inthiscaseitiscon-venienttodeterminefocalmechanismsoftheseeventsbyusingshortperiodPandSwavedataj.Focalmechanismsolutionsofsmallearthquakesin5regions,i.e.,Rongchang,Mabian-Muchuan,Ya¢an,BaoxingandMianzhu,whicharecoveredbytheChengduTelemeteredNetwork,areobtainedbyanalyzingthePpolarityandshortbodywaveamplitudedatarecordedinthenetworksince1992.AccordingtothemethodproposedbyGephartandForsyth(1984),basedonwelldeterminedfocalmechanismsolutionsin15sub-zonesofSichuanandYunnanarea,threeprincipalstresstensorss1,s2,ands3,insteadofaveragesofP,B,andTaxisofthesolutions,aredeterminedtorepresenttheregionalstressfielddistribution.
简介:HistoricaldataregardingZhangHeng'sseismoscopeisnotsingularproof.Actually,thefourearliesthistoricaldocuments,i.e.,ContinuationofHistoriographyofHanDynasty,HistoriographyoftheLaterHan,BookoftheLaterHanandDingRecordallhaverelevantrecordsofitsstructure,size,principle,responsetoearthquakeandactualapplications.Thesefiveaspectsaresupportedbyarchaeologicalresearch,unearthedculturalrelics,historicalearthquakesandmodernseismologicalstudy.Thesehistoricalmaterialscontainagreatdealofspecificinformationaboutthisancientseismoscope.Inconclusion,theauthenticityandreliabilityofZhangHeng'sseismoscopeareverified.
简介:ProcessofsourcedynamicsoftheJingtaiearthquake(M=6.2)Xue-BinDU(杜学彬);Zhi-DeYAN(闫志德)andMing-WuZOU(邹明武)(EarthquakeResearchInstitu...
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简介:RelationshipbetweenH2releaseandseis-micityonXiadianFaultQING-WUGAO(高清武),NILI(李霓)InstituteofGeology,ChinaSeismologicalBureau,...
简介:IonosphereicfoF2variationsareverysensitivetotheseismiceffectandresultsofionosphericperturbationsassociatedwithearthquakesseemtoveryhopefulforshort-termearthquakeprediction.OnJanuary18,2011at20:23UTagreatearthquake(M=7.2)occurredinDalbandin(28.73°N,63.92°E),Pakistan.Inthisstudy,wehavetriedtofindoutthefeaturesofpre-earthquakeionosphericanomaliesbyusingthehourlydaytime(08.00a.m.-05.00p.m.)dataofcriticalfrequency(foF2)obtainedbythreeverticalsoundingstationsinstalledinIslamabad(33.78°N,73.06°E),Multan(32.26°N,71.51°E)andKarachi(24.89°N,67.02°E),Pakistan.TheresultsshowthesignificantanomaliesoffoF2intheearthquakepreparationzoneseveraldayspriortotheDalbandinearthquake.ItisalsoobservedthattheamplitudeandfrequencyoffoF2anomaliesaremoreprominentattheneareststationtotheepicenterascomparedtothosestationsneartheoutermarginoftheearthquakepreparationzone.TheconfidencelevelforionosphericanomaliesregardingtheseismicsignaturescanbeenhancedbyaddingtheanalysisofsomeotherionospheicparametersalongwithcriticalfrequencyofthelayerF2.
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(MD)震源深度(Km)震中烈度 地震类型 1987080217071157°251°115°38′24°59′江西寻乌56178Ⅶ震群 微观震中与宏观震中不吻合,两者相距15Km左右,前者位于Ⅶ度极震区的外围的澄江附近。(图10-1)。图10-1 1987年8月2日寻乌地震等震线图二、地震烈度分布本次地震的宏观震中位于寻乌县城关北西3公里的文峰乡长举村附近,震中烈度Ⅶ度(图10-1)。Ⅶ度区(极震区):Ⅶ度等震线包围了寻乌县城关长宁镇及文峰乡的下河岭、黄坳、石圳、长溪和三标乡的的香
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(MD)震源深度(Km)震中烈度 地震类型 199206020019497117°51′24°21′117°52′24°21′龙海白水40Ⅴ199206020021107117°51′24°21′117°51′24°21′龙海白水42Ⅴ 宏观震中与微观震中非常吻合,仅稍偏东1分。两次地震前后间隔时间2分半钟,在原地重复。二、地震烈度分布地震宏观调查主要在Ⅴ、Ⅳ度区内进行,从图15-1上可以看出,Ⅳ度区内调查点相对较稀,Ⅲ度线是以电话调查为主来确定的。图15-1 1992年6月2日龙海
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(MS)震源深度(Km)震中烈度 地震类型 19950225111508118°42′24°22′晋江海外5310Ⅵ主余震型 本次地震的宏观震中,未作推断,从图面的合理性考虑,应在微观震中的北偏西10余公里处。二、地震烈度分布由于震中位于海域,离震中最近的金井围头也有20公里左右。在所有的现场调查点中,最高烈度值只有Ⅴ度,故仅勾划出一条Ⅴ度等震线(图21-1)。图21-1 1995年2月25日晋江海外地震等震线图Ⅴ度区:Ⅴ度等震线在惠安的辋川、斗尾一带入海,向西南,经过南安的洪濑,安
简介:Athree-dimensionalrigidbodyontheshapeofaparallelepipedismodelledinordertorockonasideoravertexofthebase,inordertoevaluatetheseismicresponseofrigidblockslyingonahorizontalsupport.Thecenterofmassofthebodyisconsideredaseccentricwithrespecttoitsgeometriccenter.Asseismicinput,threeItalianrecordedaccelerograms,withdifferentspectralcontent,areused.Thestudyismainlyconductedtohighlightthedifferencesbetweentheseismicresponseof2Dand3Dmodelsofrigidblocks,withtheaimtounderstandif,insomecases,theuseofthe3Dmodelofrigidblockisrequiredtoobtainsaferresults.Infact,theoutcomesshowthatinsomerangesofthegeometricalandmechanicalparametersthatcharacterizetheexcitationandthebody,atwo-dimensionalmodel,whichisnotabletoconsiderthe3Drockingonavertex,canprovideunsaferesults.Inparticular,itisfoundthattheoverturningprocessofthethree-dimensionalblockcanoccurunderexcitationswhicharelowerthanthosewhichoverturnacorrespondingtwo-dimensionalblock.
简介:一个方法被建议在设计实践为使用估计地震soil-structure-interaction(SSI)效果。它对受到的2D结构适用垂直地事件砍波浪由同质的一半空间支持了。自从它保留简洁,方法是吸引人的光谱途径,克服一些困难和存在古典技术的不确,然而,它考虑身体上一致的刺激。简洁的这水平通过回答被完成能被用于免费地的5%阻尼反应系列产出设计的系列修正因素光谱考虑散布运动的纵标由相互作用效果介绍了。修正因素在结构的相对排水量和免费地的运动之间的转移功能(TF)是代表性的,它以它的最大的振幅被描述并且联系了频率。由练习工程师计算修正因素的表情被建议用实际结构的576盒子代表在参量的研究之上基于。方法在跨越大量普通基本颤动时期的10种情况中被测试。
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(MS)震源深度(Km)震中烈度 地震类型 199202181916139119°40′25°01′南日岛东南5215Ⅵ孤立型 地震发生于海中,未能确定宏观震中,震中烈度亦为经验估计。二、地震烈度分布地震宏观调查工作仅限于陆地上进行,最高烈度为Ⅴ度,等震线呈向北西突出的弧形(见图13-1)。图13-1 1992年2月18日南日岛地震等震线图 Ⅴ度区:Ⅴ度等震线北起平潭岛南端的钱便澳,向西经过福清东瀚南侧,再逐渐向南拐,通过莆田埭头的汀港,到平海东面入海。在Ⅴ度区内,室内的人普遍感到
简介:Inthispaper,weproposeanearlyanalyticexponentialtimedifference(NETD)methodforsolvingthe2Dacousticandelasticwaveequations.Inthismethod,weusethenearlyanalyticdiscreteoperatortoapproximatethehigh-orderspatialdifferentialoperatorsandtransformtheseismicwaveequationsintosemi-discreteordinarydifferentialequations(ODEs).Then,theconvertedODEsystemissolvedbytheexponentialtimedifference(ETD)method.WeinvestigatethepropertiesofNETDindetail,includingthestabilityconditionfor1-Dand2-Dcases,thetheoreticalandrelativeerrors,thenumericaldispersionrelationforthe2-Dacousticcase,andthecomputationalefficiency.Inordertofurthervalidatethemethod,weapplyittosimulatingacoustic/elasticwavepropagationinmultilayermodelswhichhavestrongcontrastsandcomplexheterogeneousmedia,e.g.,theSEGmodelandtheMarmousimodel.Fromourtheoreticalanalysesandnumericalresults,theNETDcansuppressnumericaldispersioneffectivelybyusingthedisplacementandgradienttoapproximatethehigh-orderspatialderivatives.Inaddition,becauseNETDisbasedonthestructureoftheLiegroupmethodwhichpreservesthequantitativepropertiesofdifferentialequations,itcanachievemoreaccurateresultsthantheclassicalmethods.