Seismicity before and after the two great Sumatra earthquakes of 2004 and 2005     

Sławomir Jerzy Gibowicz  Wojciech Dębski 《Acta Geophysica》2006,54(4):343-360

The Harvard CMT catalogue contains 481 shallow earthquakes that occurred between 1 January 1977 and 30 November 2005 within a broad region defined by the geographical latitude from 3°S to 14°N and by the longitude from 91°E to 102°E. There are 230 events that occurred before the great earthquake of 26 December 2004. Their surface distribution is not uniform and the source area of the 2004 great event appears as an area of seismic quiescence with a radius of about 100 km. There are 186 events that occurred between the two great earthquakes of 26 December 2004 and 28 March 2005. Practically all of them are located to the northwest from the great earthquake of 2005, that in turn was followed by 63 events, mostly located to the southeast. The cumulative seismic moment from earthquakes before the occurrence of the great event of 2004 increased rather regularly with time, with sudden increase about twenty years and two years before the occurrence of the great event. The seismic moment of earthquakes between the two great events increased rapidly during the first ten-fifteen days, then flattened out and increased slowly with time. After the great event of 2005 the seismic moment shows quiet increase during some 115 days, then sudden jump, followed by very small activity till the end of our observations. From the spatial distribution of seismic moment of earthquakes that occurred before the great event of 2004 it follows that its largest release appeared to the southeast from the great event, around the rupture area of the great earthquake of 2005. The largest release of seismic moment from earthquakes between the two great events is observed in the vicinity of the 2004 event and further up to the north. The seismic moment from earthquakes that occurred after the great event of 2005 was mostly released in its vicinity and further down to the south.  相似文献   

云南地区地震视应变时空演变与强震发震地区的对应关系   总被引：3，自引：0，他引：3  

张彬  杨选辉  易志刚  孙小龙 《中国地震》2006,22(4):364-372

在前人研究的基础上，利用云南及周边地区的地震资料，研究了1970年以来云南地区地震视应变场的分布和时空演化特征。结果表明，云南地区地震视应变的时空演变与强震具有较好的对应关系。在所研究的9个强震中，8个震前出现地震视应变异常区，5个发生在异常区内，3个发生在异常区附近。最后，对研究结果进行了初步论证。  相似文献   

鲜水河断裂带北西段不同破裂源强震震级（M≥67）及复发间隔研究   总被引：1，自引：0，他引：1       下载免费PDF全文

冉洪流  何宏林 《地球物理学报》2006,49(1):153-161

鲜水河断裂带是四川西部一条晚第四纪强烈左旋走滑活动的构造带，历史上发生多次强震. 它与西北侧的甘孜—玉树断裂带一起，构成青藏高原东部的侧向滑移构造系统中的川滇活动地块的北边界——羌塘地块的东北边界. 鲜水河断裂带北西段可以分成4个段落，每一段落均可作为一个独立的基本破裂单元而发生地震破裂，亦有可能发生不同尺度的多段联合瞧裂. 对鲜水河断裂带北西段不同尺度破裂的震级及复发间隔进行研究. 根据该地区的地质、地球物理、测量及地震等方面的资料，结合我国强震复发的特点，分析了拉分盆地内部的滑动速率分布，以确定各段落的等效长度和倾向宽度，从而建立适合我国大陆走滑断裂的面波震级与断裂发震面积的关系式；进而运用地震矩方法，考虑断层之间的相互作用，结合专家意见建立了该段的矩平衡断裂破裂模型；最后，给出了鲜水河断裂带北西段各破裂源特征化地震的复发间隔、震级大小和不确定性，以及他与中小地震的联合震级分布. 结果表明，鲜水河断裂带北西段较易发生单段破裂，复发间隔在100～150年左右.  相似文献   

1994年9月16日台湾海峡7.3级地震震源过程的研究   总被引：1，自引：1，他引：0  

林邦慧  林奕山  陈诗安  王海军 《华南地震》1998,18(1):15-26

采用数字化台网Ｐ波波形资料及台湾台网Ｐ波初动方向资料,研究了１９９４年９月１６日台湾海峡７３级地震及邻近地区（北纬２１～２６°,东经１１５～１２０°）ＭＬ≥５８级共５次地震的矩张量解及震源参数。结果表明,这次７３级地震的矩张量解以双力偶成分为主,是断层面接近ＮＷ走向的正断层。断层面的走向与大震前地震的条带分布走向及余震分布显示的破裂图象较相象,震源机制的张应力轴接近水平,近ＮＥ走向;压应力轴几乎垂直,近ＮＷＷ走向,似乎表明这次地震是受菲律海板块向欧亚板块北西向挤压的力源控制。从Ｐ轴接近竖直而Ｔ轴接近水平来看,发震断层为强烈拉张性正断层,可能还同时存在垂直向上的应力作用。其它４个强震的震源机制解与７３级大震的差别较大。这些地震震源机制解的复杂性,表明台湾海峡地震序列的发展过程比较复杂。  相似文献   

Inversion of source process and related studies of the Taiwan Strait earthquake using genetic algorithm     

Hai-Jun Wang  Bang-Hui Lin  Shi-An Chen  Yi-Shan Lin 《地震学报(英文版)》1998,11(2):141-152

Applying genetic algorithm to inversion of seismic moment tensor solution and using the data of P waveform from digital network and initial motion directions of P waves of Taiwan network stations, we studied the moment tensor solutions and focal parameters of the earthquake of M=7.3 on 16 September of 1994 in Taiwan Strait and other four quakes of M _L≥5.8 in the near region (21°–26°N, 115°–120°E). Among the five earthquakes, the quake of M=7.3 on September 16, 1994 in Taiwan Strait is the strongest one in the southeastern coast area since Nan’ao earthquake of M=7.3 in 1918. The results show that moment tensor solution of M=7.3 earthquake is mainly double-couple component, and is normal fault whose fault plane is near NW. The strike of the fault plane resembles that of the distributive bands of earthquakes before the main event and fracture pattern shown by aftershocks. The tension stress axis of focal mechanism is about horizontal, near in NE strike, the compressive stress axis is approximately vertical, near in NWW strike. It seems that this quake is controlled by the force of Philippine plate’s pressing Eurasian plate in NW direction. But from the viewpoint of P axis of near vertical and T axis of near horizontal, it is a normal fault of strong tensibility. There are relatively big difference between focal mechanism solution of this quake and those of the four other strong quakes. The complexity of source mechanism solution of these quakes represents the complexity of the process of the strait earthquake sequences. Contribution No. 98A01001, Institute of Geophysics, State Seismological Bureau, China. The subject is supported and helped by Academician Yun-Tai CHEN, Profs. Qing-Yao HONG, Zhen-Xing YAO, Tian-Yu ZHENG, Yao-Lin SHI, Ji-An XU, Bo-Shou HUANG and colleague Mei-Jian AN, Xue-Reng DING, Rui-Feng LIU. De-Chong ZHANG and Ming Li provided the digital data warm-heartedly. Lin-Ying WANG offered us the catalogue of earthquakes in southeastern coastal area in China. Xi-Li WANG and Tong-Xia BAI provided us the issued annual reports data. The authors would like to express their gratitude to all of these people. This paper is sponsored by the National Natural Science Foundation of China and Scientific and Technological Commission of Shantou, Guangdong Province.  相似文献   

Inversion of free oscillation data for an elliptical rotating earth in source moment tensor studies     

Jorge A. Mendiguren 《Pure and Applied Geophysics》1980,118(2):1192-1208

It is shown, through numerical experiments, that the effect of ignoring ellipticity and rotation of the earth when inverting free oscillation data in moment tensor studies, is to introduce spurious spectral components in the solution. For numerical simulation of the data conditions of the 1970 deep Colombian event the spurious part has isotropic and deviatoric components, besides a distortion in the phase spectra which may lead to artificial precursive source in the solution. The magnitude of the artificial isotropic component is of the order of 10% of the real source moment tensor, depending on the data set used in the inversion. Measuring the excitation of each mode at each station using the technique of integrating over the spectral peaks does not cancel completely the effect of multiplet splitting, in particular that splitting due to rotation of the earth. The effect of lateral heterogeneities was simulated by introducing arbitrary splitting parameters which produced scattering in the eigenperiods compatible with those observed. For that splitting the inversion rendered additional isotropic components.We conclude that the observed implosive precursor the the 1970 Colombian event could have been artificially introduced by ignoring rotation, ellipticity and lateral heterogeneities of the earth.A procedure to invert free oscillation data for an elliptical rotating earth is proposed. It could be applied to a laterally inhomogeneous earth if the excitation for that model could be computed. Its application to real data for the deep Colombian event indicates that we will need to improve our knowledge on the effect of rotation, ellipticity, lateral heterogeneities and anelasticity on free oscillation and their excitation in order to solve accurately for the six components of the moment tensor independently.  相似文献   

华北地区一次中尺度对流系统上方的Sprite放电现象及其对应的雷达回波和闪电特征   总被引：3，自引：3，他引：0  

王志超  杨静  陆高鹏  刘冬霞  王宇  肖现  郄秀书 《大气科学》2015,39(4):839-848

利用低光度相机首次观测到了2013年7月31日华北地区一次中尺度对流系统(MCS)上空产生的中高层Sprite放电现象。结合闪电定位、天气雷达等同步观测, 对一次MCS诱发的Sprite的形态学特征及其对应的母体闪电和雷暴系统的雷达回波特征等进行了详细分析。研究除发现了2例圆柱型、3例胡萝卜型和1例舞蹈型 Sprite外, 还发现了2例发光主体发育不完全的Y字型Sprite。估算的Sprite的底部平均高度低于61.8±3.5 km, 顶部平均高度为84.3±6.8 km。Sprite持续时间算术平均值为25.7±9.8 ms, 几何平均值为24.4 ms。Sprite的母体闪电均为正地闪, 峰值电流在+62.5～+106.2 kA之间, 算术平均值为+77.1±22.2 kA, 是本次MCS所有正地闪平均峰值电流的1.4倍。Sprite母体闪电的脉冲电荷矩变化(iCMC)在+475～+922 C km之间, 几何平均值为+571.0 C km。Sprite母体闪电发生在MCS雷达回波25～35 dBZ的层状云降水区, 弱回波(<30 dBZ)面积的突然增加对Sprite的产生有重要指示作用。Sprite易发生在MCS成熟—消散阶段正地闪比例(POP)显著增加的时段。在本次MCS消散阶段中, 有两个时间段可能有利于产生Sprite。在Sprite集中发生时间段, 北京闪电综合探测网(BLNET)探测到的正地闪比例为54.2%, 正地闪连续电流比例70.24%, 连续电流持续时间为58.17±50.31 ms, 有利于Sprite的产生。  相似文献   

时间矩在地下水相关参数确定中的应用     

李亮  陈余道  蒋亚萍 《地下水》2010,32(3):9-11

应用矩分析方法定量分析示踪剂数据需要一系列严格的步骤,包括数据标准化,浓度衰减的校正,去卷积,外推和积分。正确的分析,可以得出示踪剂扫描孔隙体积、流体几何和流体速度等场地的特殊信息,有助于了解库区边界的特征。通过实例分析,结果表明：采用时间矩方法确定地下水有关参数时,效果良好。  相似文献   

多功能旋挖钻机长螺旋钻具的研制          下载免费PDF全文

王三牛  李洪  宋刚  邵玉涛 《探矿工程》2010,37(5):45-48

通过对长螺旋钻进过程中阻力矩的计算,得出了不同直径和孔深情况下的阻力矩值,依此对长螺旋钻具的强度进行比对,给出了不同口径的长螺旋钻具参数。还介绍了长螺旋钻头的不同结构形式及配套器具,简述了多功能钻机长螺旋钻进施工工艺。  相似文献   

Parametric study for optimal design of large piled raft foundations on sand     

《Computers and Geotechnics》2014

In designing piled raft foundations, controlling the total and differential settlements as well as the induced bending moments of the raft is crucial. The majority of piled raft foundations have been designed by placing piles uniformly. In such a design method, the settlements of the piled rafts are likely to be large, which leads to an increase of the pile length and/or number of piles required to reduce the settlements. However, this increase does not satisfy the requirement for economical design. On the basis of a parametric study, this paper contributes a framework for considering an economical design methodology in which piles are placed more densely beneath the column positions when the piled raft is subjected to column loads. The analysis uses PLAXIS 3D software, and the validity of the parametric study is examined through the results of centrifuge model tests conducted by the authors. The study shows that the concentrated pile arrangement method can help to considerably reduce the total and differential settlements as well as the induced bending moments of the raft. Moreover, the effects of parameters, such as pile length, pile number, raft thickness and load types, on the piled raft behavior are investigated. This study can help practicing engineers choose pile and raft parameters in combination with the concentrated pile arrangement method to produce an economical design.  相似文献