简介：ＣｕｍｕｌａｔｉｖｅｆｒｅｑｕｅｎｃｙｂｖａｌｕｅｗｉｔｈｏｕｔｕｐｐｅｒｂｏｕｎｄｍａｇｎｉｔｕｄｅａｎｄｉｔｓｒｅｇｒｅｓｓｉｏｎｄｅｔｅｒｍｉｎａｔｉｏｎＪｉａｎ－ＷｅｎＳＨＥＮ（沈建文）（ＳｅｉｓｍｏｌｏｇｉｃａｌＢｕｒｅａｕｏｆＡｎｈｕｉＰ...

简介：利用中国数字地震台网（CDSN）的7个台站记录的2010年4月14日玉树地震的波形资料,采用功率谱方法测定相继时间间隔内较清楚地球自由振荡频谱峰的能量,并采用最小二乘拟合方法确定了相应振型的Q值。结果表明不同振型的Q值明显不同,同一振型在不同台站计算得到的Q值也有略微差异。分析认为,前者可能源于地球自由振荡振型频率和探测深度不同所致,而后者可能与地壳的横向不均匀特性有关。

简介：针对传统BP神经网络存在着容易陷入局部极小点、训练时间太长等缺点,本文采用基于浮点编码的遗传算法,对BP神经网络的初值空间进行了遗传优化。用基于浮点编码的遗传算法来优化BP神经网络的权值,可得到最佳初始权值矩阵,并按误差前向反馈算法,沿负梯度搜索进行网络学习。文中以混凝土重力坝结构作为算例,用结构的模态频率变化作为网络的输入向量,结构的损伤位置作为输出向量,对网络进行了训练。仿真结果表明：遗传BP神经网络的收敛和诊断能力优于传统BP神经网络,可有效地运用到大坝结构的健康诊断与损伤识别中。

简介：TheTanlu(Tancheng-Lujiang)faultisoneofthemajorstructuresineasternChina,whichcutsacrossdifferentblocksandcontrolsthetectonicactivity.UsingtheseismicdatafromtheChinaEarthquakeNetworksCenter,weinvestigatethespatialvariationsoftheb-valueintheDabie-Sulu(Jiangsu-Shandong)organicbeltbycalculatingtheb-valueofeachgrid(1°×1°)from1970to2010.Thestudyshowsthat:theb-valueissmallerintheTanlufaultanditsadjacentarea,whichmightsuggestthatthemajorearthquakerecurrenceperiodisrelativelylongduetothelowerfrequencyofsmallearthquakeactivity.InbothsidesofTanlufault,theb-valueishigherattheedgeofSulublockandtheeasternpartofDabieorogenicbelt.ThebvaluesarehigherinNorthChinacentralorogenicbelt,andsmallearthquakeactivitywhichoccurredalongthecentralorogenicbeltisfrequent.Additionally,combinedwithgeologicalandgeophysicalstudy,wefindthattheb-valuehasacertaincorrespondencerelationshipwiththelithologicdistribution,whichinformsusthatseismicactivityfeaturesarecloselyrelatedtotheinhomogeneousmediainthecrust.

简介：

简介：SeismicityoftheEarth(MC4.5)wascompiledfromNEIC,IRISandISCcataloguesandusedtocomputeb-valuebasedonvarioustimewindows.Itisfoundthatcontinuouscyclicb-variationsoccuronbothlongandshorttimescales,thelatterbeingofmuchhighervalueandsometimesinexcessof0.7oftheabsoluteb-value.Thesevariationsoccurnotonlyyearlyormonthly,butalsodaily.Beforetheoccurrenceoflargeearthquakes,b-valuesstartincreasingwithvariablegradientsthatareaffectedbyforeshocks.Insomecases,thegradientisreducedtozeroortoanegativevalueafewdaysbeforetheearthquakeoccurrence.Ingeneral,calculatedb-valuesattainmaxima1daybeforelargeearthquakesandminimasoonaftertheiroccurrence.Bothlinearregressionandmaximumlikelihoodmethodsgivecorrelatable,butvariableresults.Itisfoundthatanexpandingtimewindowtechniquefromafixedstartingpointismoreeffectiveinthestudyofb-variations.Thecalculatedb-variationsforthewholeEarth,itshemispheres,quadrantsandtheepicentralregionsofsomelargeearthquakesareofbothlocalandregionalcharacter,whichmayindicatethatinsuchcases,thegeodynamicprocessesactingwithinacertainregionhaveamuchregionaleffectwithintheEarth.Theb-variationshavelongbeenknowntovarywithanumberoflocalandregionalfactorsincludingtectonicstresses.Theresultsreportedhereindicatethatgeotectonicstressremainsthemostsignificantfactorthatcontrolsb-variations.ItisfoundthatforearthquakeswithMwC7,anincreaseofabout0.20intheb-valueimpliesastressincreasethatwillresultinanearthquakewithamagnitudeoneunithigher.

简介：DearContributors,ReadersandFriends:2011milestonesthetenthanniversaryoftheJournalofEarthquakeEngineeringandEngineeringVibration.wefirstwanttotakethisopportunitytoexpressourgratitudetothoseretiringmembersoftheEditorialBoardfortheirvaluablecontributionsinthepast,andtowelcomethosewhojoinedtheEditorialBoardthisyear.AswementionedinourmessagetoyouinDecember2010,effective20ll,thejournalisofficiallyco-sponsoredbytheHuixianEarthquake

简介：利用1980～2007年以来，青海省东部及邻区（34°～40°N，96°～104°E）ML≥2．3级地震资料进行特征参数耽值的空间扫描。结果表明，在该区域内发生的9次6．0级以上地震中有6次震前7—28个月在震中周围出现叻值异常区，并且大部分地震前的异常区存在异常出现一异常区面积扩大一面积收缩一发震的变化过程，为地震的中短期预报提供了判定依据。

简介：Inthispaper,basedonGansuDigitalSeismicNetworkdatasince1990,wecalculatedb-valueand⊿b-valueoftheneighborhoodareabeforethe2013Minxian-ZhangxianM_S6.6,earthquake.Theresultsshowthattheearthquakeoccurredatthemarginofthesignificantlylowerb-valueareainsoutheastofGansuandbeforetheearthquaketheneighborhoodareahadanobviouslyabnormal⊿b-value.Fromtheearthquakeandthespatialdistributionoflowb-value,theregionstillhasthepossibilityofgeneratingdangerousstrongearthquakes.

简介：主要对ZD8B与ZD-8地电仪在观测的精度及稳定性、动态范围、抗干扰能力等方面进行了评价，并对观测数据进行了分析，认为地电仪观测资料可作为地震预报的可靠依据之一。

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：Micro-aftershockswithmagnituderangeof1.5-4aroundtheWenchuanearthquakeepicenter,thesouthernpartoftheLongmenshanfaultzone,exhibitgoodfrequency-magnitudelinearrelationships,thusenablingb-valueanalysis.Theaverageb-valueformicro-aftershocksofM1.5-4fromJulytoDecemberof2008inourlocalstudyregionisabout0.88,similartotheb-valueforallaftershocksofM3.0-5.5fromMay,2008toMay,2009alongthewholeLongmenshanfaultzone.Thesimilaritybetweenthelocalandregionalb-valuespossiblyindicatesthatthesouthernpartoftheLongmenshanfaultzonehassimilarseismogenicenvironmenttothewholeLongmenshanfaultzone.Alternatively,itmayalsoimplythatb-valuesderivedfromalleventswithoutconsiderationofstructuralvariationcannotdiscriminatelocal-scaletectonicinformation.Thepresentstudyshowsthattheb-valuefortheWenchuanearthquakemicro-aftershocksvarieswithdifferentregions.Theb-valueinsouthwestoftheYingxiutownishigherthanthatinthenortheastoftheYingxiutown.Thehighb-valueinthesouthwestpartwheretheWenchuanearthquakemainshockhypocenterlocatedindicatesthatthecurrentstressaroundthehypocenterregionismuchlowerthanitssurroundingarea.Theb-valuesarealsodependentondepth.Atshallowdepthsof<5km,theb-valuesareverysmall(~0.4),possiblybeingrelatedtostrongwaveattenuationorstrongheterogeneityinshallowlayerswithhighcontentofporosityandfractures.Atdepthsof~5-11km,wheremostaftershocksconcentrated,theb-valuesbecomeashighas~0.9-1.0.Atthedepthbelow~11km,theb-valuesdecreasewiththedepthincreasing,beingconsistentwithincreasingtectonichomogeneityandincreasingstresswithdepth.