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简介:TheextensivedamagetobuildingscausedbytheNepalM_s8.1earthquakehasattractedmuchattentionbytheinternationalcommunity.AfterthepreliminaryscientificinvestigationsonthedifferentaffectedareasinNepal,theconstructionanddamagecharacteristicsoffivedifferenttypesofbuildingscommonlyexistinginNepalwerediscussedandthereasonsoftheirdisasterperformancewereanalyzed.Typesofbuildingsinvestigatedincludereinforcedconcrete(RC)framestructures,rubblestructures,brick-woodstructures,rawsoilstructures,andbrick-woodstructuresofhistoricbuildings.Inaddition,theweaklinksoftheseismicdesignwerepointedout,whichwasveryimportantforthepost-earthquakereconstructionandrecovery,andgaveapreliminaryexplanationsforthedamageexperienced.
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.
简介:TheregionaltectonicbackgroundandcharacteristicsofactivefaultsoftheYutianMS7.3earthquakeonFebruary12,2014arediscussedinthispaper.AftertheanalysisoftheepicenterareaoftheMS7.3earthquakein2014andthefocalmechanismsoftheformerstrongearthquakesaroundit,theauthorsdeducedthattheseismogenicfaultoftheMS7.3earthquakeistheeastbranchoftheAshikulefault.TheMS7.3earthquakein2014andtheMS7.3earthquakein2008aretwostrongearthquakeeventsonthedifferentsectionsoftheAltunTaghfault,wherethefaultbehaviorchangesfromsinistralsliptonormalfaultingbecauseoftheextensionaltaileffectsinthesouthernendoftheAltunTaghfault.ItisconcludedthatthetwoMS7.3earthquakeshavethesamedynamicsource,andtheMS7.3earthquakein2008promotedtheoccurrenceoftheMS7.3earthquakein2014.Finally,wecalculatetheCoulombstresschangetotheseismogenicfaultoftheMS7.3earthquakein2014fromtheMS7.3earthquakein2008usingthelayeredcrustmodel.TheresultalsoshowsthattheMS7.3earthquakein2008acceleratedtheoccurrenceoftheMS7.3earthquakein2014.
简介:为了核实赤峰1号井2014年初气汞异常现象,安装ATG-6138M测汞仪与原DFG-B测汞仪进行对比观测。ATG-6138M测汞仪观测到赤峰1号井房内空气汞浓度明显高于井孔内逸出汞浓度,表明观测井房可能存在汞污染问题。两台仪器同步观测井孔内逸出气汞浓度结果表明,ATG-6138M测汞仪测试结果稳定,动态清晰,而DFG-B测汞仪观测误差较大。对比DFG-B测汞仪与ATG-6138M测汞仪校准结果认为,DFG-B测汞仪已不能正常观测汞浓度的变化,存在捕汞管老化等仪器问题。综合分析表明,赤峰1号井DFG-B测汞仪存在环境汞污染和仪器老化等因素,且集气装置不符合地震行业标准技术要求,2014年初出现的气汞浓度异常信度不高,不能作为与地震孕育有关的前兆异常信息。
简介:摘要本文以京沪高速铁路5标DK1142+300处1跨128m下承式钢管混凝土系杆提篮拱桥为背景,介绍了钢管混凝土系杆提篮拱桥具体施工方法。
简介:Near-fieldstronggroundmotionsareusefulforengineeringseismologystudiesandseismicdesign,butdenseobservationnetworksofdamagingearthquakesarestillrare.Inthisstudy,basedonthestrong-motiondatafromtheMw6.6Lushanearthquake,thegroundmotionparametersindifferentspatialregionsaresystematicallyanalyzed,andthecontributionsfromdifferenteffects,likethehanging-walleffect,directivityeffect,andattenuationeffectareseparatedtotheextentpossible.DifferentengineeringparametersfromtheobservedgroundmotionsarecomparedwiththelocaldesignresponsespectraandanewattenuationrelationofWesternChina.Generalresultsindicatethatthehighfrequencygroundmotion,likethepeakgroundacceleration,ontwosidesofthefaultplaneissensitivetothehanging-walleffect,whereasthelowfrequencygroundmotion,likethelongperiodspectralacceleration,intherupturepropagationdirectionisaffectedbythedirectivityeffect.Moreover,althoughtheMw6.6Lushanearthquakeisnotalargemagnitudeevent,thespatialdifferenceofgroundmotionisstillobvious;thus,forathrustfaultingearthquake,inadditiontothehangingeffect,thedirectivityeffectshouldalsobeconsidered.
简介:OnthebasisofthepreviousstudiesofthelayeredcrustalmodelintheYutianarea,combinedwiththefieldGPScontinuousobservationdata,weroughlyestimatetheviscouscoefficientofeachlayer.Withtheviscoelastichorizontallayermodel,wecalculatetheviscoelasticco-seismicCoulombstresschangecausedbytheYutianM_S7.3earthquakes2008and2014respectively.BasedontheCoulombstresschange,usingthecalculationmethodof"direct"aftershockfrequency,wecomeupwiththetheoreticalearthquakefrequencydirectlyrelatedtothemainshockandtheco-seismicCoulombstresschangeinthestudyarea.Thenweputforwardamethod,basedonthecomparisonoftheoreticalandactualearthquakefrequencyorthecomparisonbetweentheoreticalandpracticalearthquakefrequency-distancedecaycurvefittingresiduals,toestimatethemagnitudeofamaximumsequentearthquake,directlyrelatedtothemainshockco-seismicCoulombstresschange.Resultscalculatedbydifferentmethodsshowthatthemaximumfollow-upearthquakemagnitudecausedbythecoseismicCoulombstresschangeliesfromM_S7.2toM_S7.5followingYutianM_S7.3earthquakein2008;butthatofthe2014YutianM_S7.3earthquakeisM_S6.3.TheformerisveryclosetotheYutianM_S7.3earthquakein2014.Becauseofthesamemagnitude,relativelyclosespatialdistance,shorttimeinterval,thesameregionoftheexternalforce,thestrongcorrelationbetweentwoseismictectonicandaclearstressinteraction,wethusconsiderthatthetwoYutianM_S7.3earthquakesin2008and2014constituteapairofgeneralizeddoubleshocktypeearthquake.Thisisconsistentwiththesequencetypecharacteristicofpast"doubleshock"earthquakesintheregion.Inthispaper,theinfluenceofthemagnitudelowerlimitandtheb-valueintherelationshipofG-Rontheresultsisdiscussed.Asaresult,whentheviscoelasticcoseismicCoulombstressvariationisdetermined,thelowerlimitofmagnitudehaslittleeffectonthemaximumsequentearthquakemagnitude
简介:TemporalchangesinsiteeffectsareobtainedusingtheHVSR(horizontal-to-verticalspectralratio)methodandstrongmotionrecordsaftertheMw7.6Chi-Chiearthquake,Taiwan.Seismicdatarecordedbetween1995and2010areused,comprising3,708datafrom15stationsadjacenttotheChelungpufault.Temporalfluctuationsaredeterminedbyanalyzingthesiteeffectvariationusingatime–frequencyvariation(TFV)diagrambasedontheseseismicdata.Stationsadjacenttothefaultshowsignificantdisturbancesintheresonancefrequencyat16–26Hz.StationTCU129showsa40%dropinfundamentalfrequencyafterthemainshock,andagradualreturntotheoriginalstateovernineyears.Forstationslocatedfartherfromthefaultzone,suddenchangesintectonicstressplayadominantroleintemporalchangestotheHVSR.Animpactanalysisofthedirectionalfactorconfirmsourfindingthattheproximityofthefaulttoseismicstationshasthemostinfluenceondata.
简介:采用WRF中尺度模式,对2014年6月21—22日发生在江西省的一次连续暴雨天气过程进行了数值模拟,对模式输出的物理量进行了诊断分析,并开展了江西省东北部复杂地形的敏感性试验。结果表明:1)此次暴雨天气过程是建立在低空切变线和低空急流等系统基础上的一次降水。低空急流向暴雨区输送水汽和不稳定能量,低空切变线上中尺度系统活跃,造成强烈的上升运动,θse的垂直分布结构有利于中低层气旋的发展,不稳定能量的释放是暴雨发生和维持的机制之一。2)地形对这次暴雨的强度有很大影响。武夷山脉阻挡了切变线的南压。当武夷山脉存在时,山脉北侧在西南风环境中为迎风坡(以辐合为主),山脉以南在西南风环境中为背风坡(以辐散为主)。移除武夷山脉后,其北侧和东北侧辐合减弱,南侧辐散减弱。武夷山主峰附近(117.6°E)的经向环流也表明,山脉移除后,主峰北侧(浙赣铁路沿线附近)的上升运动减弱,最终致使该地区降水减弱。