阿尔金活动断裂带的运动学和动力学特征   总被引：6，自引：0，他引：6  

柏美祥 《新疆地质》1992,(1)

位于喜马拉雅碰撞带后陆的阿尔金活动断裂带,是自西向东逐步形成的左旋走滑断裂。早期以逆冲活动为主,晚期以走滑活动为主。距今0.35Ma(中更新世)以来,平均左旋走滑速率为4.9±0.4mm/a,平均水平错动量是垂直错动量的12.3倍。晚更新世晚期至全新世时期发生过5次古地震,平均复现期为800年左右。  相似文献   

怎样正确计算b值   总被引：1，自引：0，他引：1  

孙文福  顾浩鼎 《东北地震研究》1992,(4)

在我们研究震级一频度客观分布的基础上,根据数理统计理论和大量的实际地震活动资料,对b值的正确计算问题进行了详细的讨论,结果认为最小二乘法是计算b值的最好方法。此外,还认真地研究了与b值正确计算有关的下限震级、上限震级、样本数以及震级分档区间等具体问题,并给出了它们的合理选择方法。  相似文献   

板内地震的一种发震模式     

林旭光  张昌达 《地球科学》1992,17(5):599-607

  相似文献   

断面擦痕滑动矢量法在自贡地区的应用   总被引：1，自引：0，他引：1  

何玉林 《四川地震》1991,(4):9-14

本文运用断面擦痕滑动矢量分析方法,用 Etchecopar 电算法定量反演了自贡地区的平均构造应力场。结果表明:自贡地区第四纪构造应力场曾发生过重大变化,主压应力轴方向由北西向转为北东向,垂直运动分量加大。这种变化是局部应力调整的结果,并在地表形成切割早期构造的北西向断裂。  相似文献   

估计地震能量和地震效率的构造物理方法          下载免费PDF全文

王绳祖 《地震地质》1992,14(4):325-332

根据强约束匀阻化椭圆形震源简化模型及震源参数计算原理,建立了一种由构造、介质、物理环境和驱动背景等条件估计地震能量和地震效率的构造物理方法,并针对我国28例6级以上地震进行了初步的验算。其结果表明:地震效率η为0.008～0.050;由本方法所得地震能量推算的震级,与各震例原定震级相比较,78.6％的震例震级偏差不超出±0.5级  相似文献   

利用深井观测速度型记录的最大振幅测定近震震级的一种方法     

章纯  朱元清  李慧民 《地震地磁观测与研究》1992,(6)

根据上海台网观测记录到的上海及邻近地区1985年至1990年期间179次地震事件的资料,以虹桥台、南汇台的两口深井观测地震记录为例,探讨如何利用深井观测速度型记录的最大振幅来测定近震震级。对于400公里以内的地震,本文根据统计规律,提出:在已知系统速度灵敏度K,地震记录的最大振幅A和地震震中距Δ的前提下,速度型记录的近震震级可以表示为M_v=logA/K+blog(Δ)+c误差分析表明,M_v与M_L是比较接近的,结果是可用的。  相似文献   

金沙江断裂带新活动和巴塘6.5级地震震中的确定     

伍先国  蔡长星 《地震研究》1992,15(4):401-410

作者通过对区域地质调查资料的分析研究和实地考察,对金沙江断裂带的展布范围进行了划分,认为金沙江断裂带是川西规模巨大的断裂带,从地震活动、断裂地貌特征、水系扭曲、第四纪地层形变和温泉沿断裂分布等表明它是一个活动断裂带。通过对历史地震实地访问调查,获得了1923年巴塘6.5级地震的震害情况,并发现了这次地震在地表所产生的地裂缝,从而确定了这次地震的宏观震中位置,探讨了地震与断裂的关系。无疑对金沙江断裂带活动性的认识、地震预报和地震烈度区划工作具有现实意义。  相似文献   

Space-time correlations ofb values with stress release     

T. I. Urbancic  C-I. Trifu  J. M. Long  R. P. Young 《Pure and Applied Geophysics》1992,139(3-4):449-462

A total of 1503 events for a 2-month period associated with am _N 2.6 rockburst is investigated for possible space-time correlations between low magnitude (–1.1 to –0.4)b values and several estimates of stress (static stress drop, apparent stress, and dynamic stress). Spatial variations of decreasingb values were found to be well correlated with increasing stress release estimates for time intervals prior to the rockburst and following the aftershock sequence. The strongest correlation tob value was with the dynamic stress drop, having correlation coefficients of 0.87 and 0.79 for the two intervals, respectively. The rockburst was found to actually occur at the intersection of the spatial coordinates corresponding to the largest gradient inb value. Based on these correlations, we conclude that the low magnitude seismicity is an indicator of the stress state within the rock mass, and can be used to study and forecast stress patterns in the vicinity of an impending major event. Time variations, however, did not show the same clear correlations and these are discussed in terms of departure from steady state conditions. Regardless, our results favour the use ofb values in a spatial, context rather than in a time analysis approach, and we consider thatb values provide valuable information regarding the changing stress conditions within the seismogenic volume.  相似文献   

泾阳地震台近震震级（Ml）误差分析及其校正     

毛娟 《地震地磁观测与研究》1992,13(2):39-43

本文对泾阳台1982—1989年457次单台近震震级同省台网近震震级对比进行统计分析,并对1990年1月—8月50次记录到的近震进行检验,得到泾阳台测定M_L震级精度为±0.205,经校正后的精度为±0.129,下降率为37.1％,尤其震中距小于100km的地方震,单台震级精度为±0.527,校正后震级精度为土0.156,下降率为70.4％。  相似文献   

ESTIMATING PRESENT SLIP RATE OF THE FAULTS IN THE WEIHE GRABEN USING ENVISAT ASAR DATA          下载免费PDF全文

CHEN Jian-long  ZHANG Dong-li  ZHOU Yu 《地震地质》1979,42(2):333-345

Most great(M≥8)earthquakes during modern times have occurred in interplate regions or major continental collision zones, such as Sumatra, the Japanese island arc or the San Andreas fault zone. Continental faults slip at a much lower rate than boundary faults, but they also have the potential of generating large earthquakes. For example, the 2008 Wenchuan earthquake with a magnitude of 7.9, the slip rate of seismic fault is less than 3mm/a. They also have the potential to be significantly deadlier than those on plate boundaries because of the long repeat times and lack of preparedness. The January 23rd 1556 Huaxian earthquake in Shaanxi Province, central China, is the deadliest in history with an estimated death toll of ~830 000 from building collapse, land-sliding, famine, and disease. The earthquake occurred in the graben of the Weihe River.
The Weihe Graben in Shaanxi Province has recorded multiple earthquakes in history, whereas most active faults within the graben have a low slip rate over geological times (~1mm/a). The slip rate of faults is an important parameter for assessing the risk of earthquakes and the interval between major earthquake recurrences. In order to obtain the quantitative information of faults slip rate, traditional geological methods or geodetic observation techniques can be used. Interferometric synthetic aperture radar(InSAR), as a modern geodetic observation technology, has the characteristics of all-weather and day-and-night imaging capability, wide spatial coverage, fine resolution, and high measurement accuracy. InSAR offers the potential to measure interseismic slip rates on faults at a resolution of millimetres per year. In this study, we use InSAR data to analyze the present deformation of the Kouzhen-Guanshan, Weihe and North Qinling faults in the central part of the graben.
We collected 32 European Space Agency(ESA's)Envisat ASAR images from descending track 161 between 2003 and 2010, and processed them using ROI_PAC. The precise orbit determination from the Delft Institute for Earth Oriented Space Research(DEOS)was applied to correct for orbital effects. The topographic contribution was simulated and removed using the 90m resolution Shuttle Radar Topography Mission(SRTM)Digital Elevation Model(DEM)from CGIAR-SCI. Each interferogram was downsampled to 64 looks in the range direction (1 280m). Before phase unwrapping, a weighted power spectrum filter was applied to improve the signal-to-noise ratio. The branch-cut method was used for phase unwrapping. Phase unwrapping errors were checked by summing around a closed loop. All the major unwrapping errors were identified and corrected manually. We obtained a total of 98 interferograms with a spatial baseline of smaller than 300m, and selected 33 interferograms whose coherence is well preserved for time-series analysis. The time-series analysis was implemented using the π-RATE software package. It uses the geocoded interferograms from ROI_PAC to create a minimum spanning tree(MST)network, from which the orbital and topographically-correlated atmospheric errors are estimated. The MST network connects all epochs with the most coherent interferograms,including no closed loops of interferograms. The network approach is able to improve the estimation of orbital error by ~9% compared to the independent interferograms approach. The orbital errors are empirically modelled as planar or quadratic ramps. The topographically-correlated atmospheric correction was applied to each interferogram after having corrected for the orbital errors. Following creating a minimum spanning tree network, correcting for orbital and topographically-correlated atmospheric errors, and calculating the covariance matrix, we obtained the 7-year average slip rate of the faults that we are focused on.
Our results show that the faults across the Weihe graben all have a small slip rate of less than 2mm/a. The Kouzhen-Guanshan Fault does not show any evident deformation signal. The Weihe Fault seems to show 1mm/a normal faulting in the satellite line-of-sight direction. In addition, we find ~10mm/a surface subsidence of the Xi'an City between 2003 and 2010. We use the stable Ordos block as a reference to assess the accuracy of our InSAR time-series analysis. Assuming the Ordos block has no internal deformation, we calculated the error of the InSAR rate map to be (-0.1±1)mm/a, indicating that our result is reliable. This paper presents a preliminary result of the present deformation of the Weihe Graben. InSAR is a powerful technique for monitoring active faults on a timescale of tens of years, and can be used for seismic hazard assessment in the future.  相似文献