岫岩5.4级地震前后拐角频率比的变化特征

本文在利用多台研究1999年11月29日和2000年1月12日发生在辽宁岫岩Ms5.4级和5.1级地震前拐角频率比随时间变化的基础上,对岫岩、营口、苏家屯、丹东、宽甸、北镇、新民单台记录的纵横波拐角频率比fcp/fcs做了比较详细的波谱分析。结果表明:在震中距小于200 km以内的不同方向的台站,记录到的地震波拐角频率比值在5.4级前和后均出现不同程度的异常显示,能够捕捉到一些带有短临性质的信息,不过,距震中较远的台站,地震波拐角频率比值在震前异常不如近台明显,表明不同距离的台站,记录的地震拐角频率比值存在着差异。     

岫岩地震序列视应力变化及其预测意义

选取辽宁省地震局沈阳数字化地震台网中的岫岩、 营口、 本溪、 北镇、 新民5个台的波形记录, 计算了1999年11月29日岫岩M_S5.4地震序列视应力值。 5个台资料的计算结果具有很好的一致性, 即岫岩序列的视应力变化特征具有显著的共性特征: 震前低视应力阶段、 震时高视应力阶段和震后逐渐降低的调整至稳定阶段, M_S5.4主震和5.1级最大强余震前视应力升高, 表明视应力可作为中强震及震后地震趋势预测的判定依据。     

利用纵、横波的拐角频率比值和位移谱零频极限比值计算波速比——以芦山M_S7.0地震序列为例

使用区域固定台网数字地震记录资料,计算2013年4月20日四川芦山MS7.0地震余震序列的震源谱参数,通过纵、横波的拐角频率比值和纵、横波位移谱零频极限比值计算波速比。结果显示:1拐角频率比值得到的波速比平均值约为1.27,零频极限比值得到的波速比平均值约为1.67,零频极限比值得到的结果更接近泊松介质的波速比1.73;2两种方法得到的波速比变化趋势基本一致:在主震后均处于较低异常水平,最后一个MS5.4余震后,波速比回返升高;3零频极限比值得到的波速比异常形态较明显,在3个MS5.4余震前都呈现出"降低-回返"的过程,在回返之后发生最大余震;4在数据处理过程中,是否对介质做非弹性衰减校正对两种方法的结果影响不大;5单台波速比与多台波速比的变化趋势基本一致。     

利用重复地震研究新疆阿合奇—伽师—乌恰地区地壳介质变化

利用射线追踪方法对新疆伽师地区的重复地震进行位置归一处理,提高走时精度以达到观测伽师—乌恰和伽师—阿合奇地区地壳介质变化的目的。计算了伽师地区2005年1月至2011年3月ML≥2.5重复地震序列经射线追踪和波形互相关方法校正后的P波走时差。结果显示,在2009年2月20日柯坪5.4级地震前阿合奇台的记录观察到该地区短期的地壳介质速度明显升高现象,2010年6月10日乌恰5.2级地震前乌恰台也同样记录观察到该现象。     

含流体孔隙介质中面波的传播特性及应用

基于单相介质中地震波理论的高频面波法已广泛应用于求取浅地表S波的速度.然而水文地质条件表明,普遍的浅地表地球介质富含孔隙.孔隙中充填的流体会显著地影响面波在浅地表的传播,进而造成频散和衰减的变化.本文研究了地震勘探频段内针对含流体孔隙介质边界条件的面波的传播特性.孔隙流体在自由表面存在完全疏通、完全闭合以及部分疏通的情况.孔隙单一流体饱和时,任何流体边界条件下存在R1模式波,与弹性介质中的Rayleigh波类似,相速度稍小于S波并在地震记录中显示强振幅.由于介质的内在衰减,R1在均匀半空间中也存在频散,相速度和衰减在不同流体边界下存在差异.Biot固流耦合系数(孔隙流体黏滞度与骨架渗透率之比)控制频散的特征频率,高耦合系数会在地震勘探频带内明显消除这种差异.介质的迂曲度等其他物性参数对不同流体边界下的R1波的影响也有不同的敏感度.完全闭合和部分疏通流体边界下存在R2模式波,相速度略低于慢P波.在多数条件下,如慢P波在时频响应中难以观察到.但是在耦合系数较低时会显现,一定条件下甚至会以非物理波形式接收R1波的辐射,显示强振幅.浅表风化层低速带存在,震源激发时的运动会显著影响面波的传播.对于接收点径向运动会造成面波的Doppler频移,横向运动会造成面波的时频畸变.孔隙存在多相流体时,中观尺度下不均匀斑块饱和能很好地解释体波在地震频带内的衰减.快P波受到斑块饱和显著影响,R1波与快P波有更明显关联,与完全饱和模型中不同,也更易于等效模型建立.频散特征频率受孔隙空间不同流体成分比例变化的控制,为面波方法探测浅地表流体分布与迁移提供可能性.通常情况孔隙介质频散特征频率较高,标准线性黏弹性固体可以在相对低频的地震勘探频带内等效表征孔隙介质中R1波的传播特征,特别在时域,可在面波成像反演建模中应用.     

DK1地震仪的面波震级起算函数研究di

使用1987～1993年DK1地震仪的地震记录，以国际地震中心(ISC)MS震级为标准震级，根据误差理论用最小二乘法拟合导出DK1地震仪面波震级起算函数．又从起算函数物理意义出发，根据成层介质中面波传播理论，考虑到地震波的频散、介质的吸收、地球介质与DK1地震仪所组成的线性滤波器对面波振幅和周期的影响，并假定面波最大振幅对应于Airy相，导出了DK1地震仪测定面波震级的起算函数． 使用本文导出的起算函数，不附加任何校正值．通过315个地震，对36个速报台的单台DK1面波震级和DK1速报台网的面波震级测定误差检验，结果表明，DK1面波震级MS(DK1)与国际地震中心(ISC)相应地震面波震级MS(ISC)之间在统计上无系统误差，平均误差接近于零．      

山西断陷带北中部介质Q值的研究

根据介质Q值理论,通过小震记录中地震直达波P波测定了山西断陷带北中部的介质Q值。从定襄、代县、灵丘、大同台的小震目录中精选出92个记录波形好的地震样本进行了Q值测定,弄清了山西断陷带北中部的介质Q值分布情况,得出了Q值相对较高的区和点,这为未来山西中强地震的预报提供了一个重要依据。     

岫岩5.4和5.1级地震前波谱异常特征研究

使用辽宁数字地震台网1999年11月9日至2000年1月10日记录的52次地震共360余条数字化波形事件, 采用PITSA软件, 对发生在岫岩5.4级地震的27个前震和5.4级地震后的5.1级地震(最大余震)前25个余震的纵、 横波拐角频率比值f_cp/f_cs进行了研究。 结果表明: 在岫岩5.4级和5.1级地震前的纵波和横波拐角频率比值f_cp/f_cs, 在2次较大地震前均出现较明显的下降异常, 此异常可作为今后地震预测可能的参考与临震判断的依据。     

水库诱发地震中水库水体下方的地震波速比

以大桥水库MS4.6诱发地震和紫坪铺水库ML2.5诱发震群为例,研究了穿过水体下方的地震波的波速比在地震前后的变化.由彝海子台记录的穿过大桥水库水体下方的地震波所计算的波速比,在蓄水后4.6级主震前存在高值异常,反映库水对波速比有影响;由八角台记录的穿过紫坪铺水库水体下方的地震波所计算的波速比显示,在2006年8月28日后一时段库区东北部出现微小的波速比高值异常,结果于2006年10月至2007年2月在八角台附近的汶川水磨发生了2.5级水库诱发震群.因此认为,根据穿过水库水体下方的地震波射线计算的单台波速比,能够反映地震孕育过程中震源及周围地区介质特性的改变,可作为监测水库地震的一种手段.     

我国东南地区πg波的频散特征

本文利用1987年8月在江西省寻乌发生的三次5.0级以上地震的记录资料,讨论了我国东南地区π_g波的传播特征。结果表明:π_g波的初至波速为6.00km/s,与Press的结果相近;π_g波有明显的频散特征,其卓越周期为0.6—0.8秒,较多表现为正常频散,同时也有少量表现为反常频散,由π_g波的波数及波峰的水平合成矢量得到的振幅辐射图象,基本上与弱非均匀介质辐射图象相近;π_g波各波数水平到时与垂直到时存在明显的到时差。     

Archaea,the tree of life,and cellular evolution in eukaryotes

The early history of life harbours many unresolved evolutionary questions, none more important than the genomic origin and cellular evolution of eukaryotes. An issue central to eukaryote origin concerns the position of eukaryotes in the tree of life and the relationship of the host lineage that acquired the mitochondrion some two billion years ago to lineages of modern-day archaea. Recent analyses indicate that the host lineage branches within the Archaea, prompting the search for novel archaeal lineages that can improve our understanding of the cellular evolution of eukaryotes. Here we give a brief review of the studies on Archaea, the tree of life and the cellular evolution of eukaryotes, which is followed by an overview of recent progress fueled by new genomic technologies and recent status of archaeal research in China. Future directions for the study of early evolution are considered.     

Knowledge,transparency, and refutability in groundwater models,an example from the Death Valley regional groundwater flow system

This work demonstrates how available knowledge can be used to build more transparent and refutable computer models of groundwater systems. The Death Valley regional groundwater flow system, which surrounds a proposed site for a high level nuclear waste repository of the United States of America, and the Nevada National Security Site (NNSS), where nuclear weapons were tested, is used to explore model adequacy, identify parameters important to (and informed by) observations, and identify existing old and potential new observations important to predictions. Model development is pursued using a set of fundamental questions addressed with carefully designed metrics. Critical methods include using a hydrogeologic model, managing model nonlinearity by designing models that are robust while maintaining realism, using error-based weighting to combine disparate types of data, and identifying important and unimportant parameters and observations and optimizing parameter values with computationally frugal schemes. The frugal schemes employed in this study require relatively few (10–1000 s), parallelizable model runs. This is beneficial because models able to approximate the complex site geology defensibly tend to have high computational cost. The issue of model defensibility is particularly important given the contentious political issues involved.     

Pb isotope geochemistry of lead,zinc, gold and silver deposit clustered region,Liaodong rift zone,northeastern China

As one of the important deposit-clustered regionsof China, the Liaodong (eastern Liaoning Province)rift zone contains many large lead, zinc, gold, boron,magnesite and talc ore deposits with a long mininghistory. Recently, large-scale Xiaotongjiapuzi gold andGaojiapuzi silver deposits were discovered in the re-gion. Much work on the origin of these deposits hasbeen carried out, however, the discrepancy on the ageand the metal source of the deposits still rem- discu…     

ANALYSIS ON DISASTER CHARACTERISTICS OF THE MS5.4 CANGWU,GUANGXI EARTHQUAKE,JULY, 31th, 2016

On July 31^th, 2016, a moderately strong earthquake of M_S5.4 hit the Cangwu County in Guangxi Zhuang Autonomous Region. The focal depth of this earthquake is about 10 kilometers. This earthquake occurred in the junction area of Guangxi Zhuang Autonomous Region, Hunan Province and Guangdong Province. Nanning, Guangzhou, Shenzhen and other cities felt this earthquake. The Cangwu County disaster area is unique in terms of geographical position, tectonic geology, landform, economic development situation, population distribution and climate condition, etc. Based on the investigation to the earthquake hit area, and the analysis of its special natural environment, social economical conditions and humanities, seven general disaster characteristics of the Cangwu M_S5.4 earthquake are summarized from the point of view of earthquake disaster emergency rescue and reconstruction. namely, the low population density in the disaster area, the single building structure type and the low-level economic development, the short duration of ground motion, the small number and low magnitude of aftershocks, no large landslide, debris flow and other secondary geological disasters caused by this earthquake, the area is prone to typhoon and other climate disasters which are likely to aggravate earthquake disaster, and the earthquake occurred in an area of weak seismicity in South China. This paper introduces the basic situation of the M_S5.4 Cangwu earthquake and analyzes the seven disaster characteristics of this earthquake. In order to better respond to moderate-strong earthquake in weak seismicity regions of South China, this paper summarizes some experience and revelations about the earthquake in the M_S5.4 Cangwu earthquake emergency response process, and puts forward some corresponding countermeasures of earthquake disaster reduction in weak seismicity regions in southern China. In the future work, we should pay more attention to pre-disaster prevention, and strengthen earthquake-monitoring capability. In order to reduce the casualties caused by collapse of houses, we should improve the seismic fortification standards of houses, carry out relevant researches on earthquake damage prevention measures of karst areas. And in order to carry out comprehensive disaster reduction, we should strengthen cooperation with the meteorological department, and carry out more comprehensive earthquake emergency drills.     

河南及邻区ML≥4.7地震前b值c值d值综合异常识别

从ML≥4.7地震前震中附近地区中小地震活动呈现增强过程及地震活动参数表现的异常现象出发,对河南及邻区1970年至今ML≥4.7地震前b值、c值、d值的综合异常进行了分析,认为其对提高地震分析预报的可信度,较好地避免单方法预报的虚报、漏报有一定的效果。     

2007年宁洱6.4级地震余震序列尾波QC值研究

基于Aki和Chouet的地方震尾波单次散射模型,利用思茅台记录到的2007年云南宁洱6.4地震余震的数字化波形观测资料,测量了震源区尾波Qc(f)值。当中心频率为1.5Hz时,宁洱地区的尾波Qc值在51～147之间,平均值为79,尾波的振幅衰减率βc(f)在0.014～0.039之间,平均值为0.028;测量得到该地区尾波Qc值与频率f的关系为Qc(f)=53f0.88;尾波波源因子与震级成正比关系,满足关系lgA0=1.51ML-0.94;测量结果显示宁洱地震余震序列的尾波值Qc较低,表明宁洱震源区属于构造运动较为活跃区。     

重庆市江北5.2,5.4级地震的地质构造背景

1989年11月20日的重庆市江北5.2级、5.4级地震。被认为是处于四川东部台拗的一系列线状、弧形状构造在现代近东西向应力作用下,这一发育极为完整的构造再次活动的结果。其具体背景构造有华蓥山构造带、七曜山—金佛山构造带和长寿—南桐构造带。它们是该区中强地震的直接控震构造。这些构造带控制了该区的岩性、构造和应力的积累、释放。故认为地震的发生正是上述构造带相继多次活动,从而导致江北地区地腹构造发生粘滑性活动的结果。     

Geology and isotopic composition of helium,neon, xenon and metallogenic age of the Jinding and Baiyangping ore deposits,northwest Yunnan,China

TheJindingoredeposit,locatedinthenorthwestYunnanProvince,isthelargestPb-Zndeposit(Pb Zn>15Mt1),averagingZn=6.08%andPb/Zn=1/4.7)inChinaatpresent.Toitsnorth,alargeCu-Co-AgdeposithasbeenfoundatBaiyangpingrecently1).TheJindingPb-Zndepositishostedinsandstonesa…     

Spatial damage distribution of August 16,2003,Inner Mongolia,China,M_S=5.9 earth-quake and analysis

Introduction The ground motion is generally estimated by attenuation relation in seismic hazard assesment.The attenuation relation is usually the function of earthquake magnitude and distance.Actually the focal mechanism and other source parameters may also have significant impacts on the ground motion,especially in the near-source region.Recent post-earthquake investigations show that the damages have close relation with the closest fault-plane distance.On August16,2003,a MS=5.9earthquake o…     

Magma traps: Part I,theory

The role of the buoyancy barrier of the stratified crust in controlling the ascent of magmas is represented by a model which operates close to lithostatic equilibrium and in which fractional crystallization of the magma or partial melting of the ambient rock can occur. The density structure of the crust has a powerful effect in trapping magma and thereby in controlling the occurrence of high level geothermal systems. The model is tested in Part II (this volume).