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汶川8.0级地震前紫坪铺水库小震活动及震源参数研究 总被引：2，自引：0，他引：2
利用区域和水库地震台网记录的数字地震波资料,研究了汶川8.0级地震前的2000年1月1日～2008年5月11日紫坪铺水库区的地震活动及震源参数.结果表明:汶川8.0级地震前该区域小震活动持续,地震活动水平为M_L2～3,自2005年9月紫坪铺水库蓄水以来,特别是2008年2月地震活动明显增加,但从长期的序列来看,地震活动频次和强度仍在区域地震活动的正常起伏范围.汶川8.0级地震发生前近3个月内,中小地震的视应力差值△σ_(app)普遍大于0,计算得到的视应力总大于其拟合值.汶川8.0级地震震中位于低应力区,而相对较高的视应力差值分布在震中以东地区,局部出现视应力增加的现象. 相似文献
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汶川、 芦山地震前后四川地区应力场时空演化 总被引：1，自引：0，他引：1
基于四川地区2000年1月~2014年6月ML≥3.0地震震源机制解, 首先分析了四川地区各次级地块和不同断裂带的地震震源机制类型及整体应力场特征, 其次以汶川8.0级、 芦山7.0级地震为例, 研究两次强震发生前后四川各次级地块的主压应力时空演化特征。 获得的主要认识为: ① 四川各次级地块的地震震源机制比较紊乱, 反映了块体内部构造的复杂性, 而断裂带的地震震源机制则相对比较单一, 与其运动类型一致; ② 四川各次级地块及断裂带的整体应力方向比较一致, 优势方位呈现NW和NWW向, 倾角接近水平; ③ 汶川8.0级、 芦山7.0级地震发生前, 震中所在的龙门山断裂带中南段及川青地块的主压应力方位均出现过较好的一致性, 而在芦山地震后, 龙门山断裂带及川青、 川中地块的主压应力优势方位则转变为NE向。 相似文献
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汶川8.0级地震前龙门山断裂带的地震活动性和构造应力场特征 总被引：7，自引：0，他引：7
研究了2008年5月12日汶川8.0级地震前龙门山断裂带及其附近地区的地震活动.利用区域地震台网和流动测震台的数字地震波资料,测定了震源机制解.结果表明,震中所在的龙门山断裂带震前地震活动平稳,未出现显著异常增强或平静现象.根据汶川8.0级地震前地震活动求出的震源机制解,其主压应力P轴方位为WNE——ESE向,震源断层面呈NE向与NW 向两组节面走向.其中NE向节面呈N50deg;——70deg;E,断面倾角均陡,达60deg;——70deg;,震源力学作用方式多呈逆倾型,少部分呈走滑型．震前地震活动呈现的主压应力方位、震源断面走向及其错动类型,与汶川8.0级地震给出的解是一致的.巨大地震发生前沿龙门山断裂带微破裂呈现的平均应力场与主震一致．起始破裂区东侧20km内是紫坪铺水库水域区,这一区域发生小震活动增加的现象处于水库放水的卸载阶段.本文研究了汶川8.0级地震起始破裂区附近的小震活动,其震源参数表明,震源位于8.0级地震之上的5——14km深度,其震源参数与8.0级地震给出的解也是一致的． 相似文献
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根据P波、S波的振幅并结合部分记录清晰的P波初动资料，求得1994——2005年川滇地区4个次级地块，即川青地块、雅江地块、川中地块和滇中地块2.5级以上有良好地震波记录的925次地震的震源机制解. 结合已取得的中强地震的震源机制解资料，研究了上述4个次级地块的应力场特征及震源断层的错动类型. 其P轴优势方位分布:川青地块为EW方向，雅江地块、川中地块、滇中地块为ESE或SE方位. 根据大量震源机制解资料， 编程计算了各地块的平均应力张量， 即主应力sigma;1, sigma;2, sigma;3的方向. 定义了单个震源机制解的力轴与平均应力张量的差异， 或称震源机制解的一致性参数， 进而分析了川滇4个次级地块的值和震源断层错动类型的分布及随时间的变化. 通过次级地块大量区域小震震源机制解的测定，可以给出动态应力场和震源断层错动方式的变化信息. 相似文献
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利用成都数字地震台网的波形记录资料，研究了四川地区地震辐射能量〖WTHX〗E〖WTBZ〗s、σapp视应力等震源参数及相互关系.对时域波形数字记录首先进行数据处理，包括带通滤波，快速富氏变换，扣除仪器幅频特性；经反变换，回到时间域，给出数字波形时间序列，选取所有方向的整个p波和s波段数据；二次变换到频率域内计算速度和地动位移的功率谱积分，进而求得各台站记录的地震波辐射能量和视应力等震源参数.研究了2000年5月到2004年8月成都数字地震台网记录的224个3级以上地震的震源参数.四川地区地震辐射能量〖WTHX〗E〖WTBZ〗s与地震矩M0，应力降Δσ与视应力σapp，视应力σapp与震级ML大体成正比.其中地震视应力σapp与震级分布数据较宽，地震视应力与破裂尺度ra的关系也较分散.同时研究了四川地区近年视应力σapp的空间分布.方法是将计算的σapp值在一定空间邻域内作平均，从而绘出等值线.分析结果表明，σapp值的相对高值区分布在四川南部的川滇交界和北部的川甘交界一带.同时研究了四川地区地震视应力值的时间分布.最后对中小地震视应力σapp及其他震源谱参数的意义作了讨论. 相似文献
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汶川8.0级地震前四川地区地震视应力时空变化特征 总被引：17，自引：0，他引：17
本文根据Brune模式,在近震源条件下,利用中国数字遥测地震台网观测的波形资料,测定了2000年5月至2008年4月四川地区439次ML≥3.0地震的视应力值,给出了2008年5月12日汶川8.0级地震前四川地区视应力空间分布图象,分析了四川地区、龙门山断裂带以及龙门山断裂带上小震频次高值区视应力随时间变化过程。结果表明:①汶川地震前,视应力较高的地震主要集中在四川南部的川、滇交界地区;②2001—2006年,四川地区视应力随时间的变化表现为突升突降型变化形态,且视应力高值点有逐渐增大的现象,从2007年初至2008年初视应力在较低水平呈缓慢下降,临近汶川地震前有小幅升高变化;③龙门山断裂带上视应力在2004年中至2005年初曾出现过较为明显的、短暂的上升—下降变化过程。而Δσapp值的变化则相对复杂,出现过二次上升—下降变化过程;④龙门山断裂带上小震频次高值区视应力在2003—2005年间,曾出现过二次较为明显的上升—下降变化过程,临震前,视应力出现突然上升。而Δσapp值随时间的变化则主要表现为2003—2004年的上升和其后的下降过程。临近地震发生前,Δσapp值也有一定幅度的上升变化。 相似文献
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利用2004年8月16日到2008年5月12日汶川8.0级地震前紫坪铺水库数字地震台网和成都数字地震台网的地震波形资料,运用振幅比方法计算了紫坪铺库区486次1.6级以上地震的震源机制参数;根据得到的震源机制参数分析了紫坪铺库区震源机制和应力场的时空变化特征。结果显示:2006—2008年紫坪铺水库水域范围内逆冲型地震很少,走滑型地震增加;距水域较远的区域逆冲型地震的比例偏高,走滑型地震没有增加;各区域的平均主压应力场的方位在汶川8.0级地震前出现了不同程度的偏转和扰动。 相似文献
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芦山地震前后龙门山断裂带南段视应力研究 总被引：1，自引：0，他引：1
利用四川台网数字地震记录资料,计算了2008年汶川地震之后、2013年芦山地震之前5年内,龙门山断裂带南段ML3.0级以上地震视应力随时间的变化,以及芦山M7.0级地震序列的视应力值及其时空分布特征.结果表明：①从芦山地震之前1年的时间开始,龙门山断裂带南段有视应力的上升过程;②芦山地震余震序列视应力存在几次比较突出的视应力与震级相关性的被打破以及视应力的突降异常,且在震后3个小时之后,视应力即有明显下降的过程;③从归准化的芦山地震序列视应力σapp的空间分布来看,视应力高值区域分布在主震的西南方向和整个余震区东南边缘,并且这两个高视应力区正好分布在该断层面与华南地块紧密接触的边缘;④主震西侧有一片视应力相对较高的区域;⑤主震以北区域的视应力则相对较低. 相似文献
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Based on the digital seismic waveform data observed from regional and reservoir seismic networks,the seismicity and source parameters in the Zipingpu reservoir area from January 1,2000 to May 11,2008 before the Wenchuan MS8.0 earthquake are studied. The analysis shows a continuous activity of small earthquakes before the Wenchuan MS8. 0 earthquake. The level of seismic activity was from ML2.0 to ML3.0 in recent years. The impoundment of Zipingpu reservoir started in September 2005 and the obvious increment of seismic activities occurred in February 2008,but according to the analysis of the longer time series,the frequency and intensity of seismic activities do not exceed its range,which means it is still a fluctuation of regional seismic activities or tectonic activity. At the same time,we also studied the spatio-temporal distribution and the change of apparent stress difference in the source region before the great earthquake,and the results show that the apparent stress values of small earthquakes are generally higher than fitted values of apparent stress in the reservoir area in the nearly three months before the Wenchuan MS8.0 earthquake. It can be seen from the spatial distribution of apparent stress difference,that the epicenter of the earthquake is located at a low stress distribution area,and the relatively high apparent stress difference is at the east of the epicenter. Apparent stress increment occurred in local areas. 相似文献
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The seismicity and tectonic stress field characteristics of the Longmenshan fault zone before the Wenchuan MS8.0 earthquake 
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下载免费PDF全文 The seismicity of Longmenshan fault zone and its vicinities before the 12 May 2008 Wenchuan MS8.0 earthquake is studied. Based on the digital seismic waveform data observed from regional seismic networks and mobile stations, the focal mechanism solutions are determined. Our analysis results show that the seismicities of Longmenshan fault zone before the 12 May 2008 Wenchuan earthquake were in stable state. No obvious phenomena of seismic activity intensifying appeared. According to focal mechanism solutions of some small earthquakes before the 12 May 2008 Wenchuan earthquake, the direction of principal compressive stress P-axis is WNW-ESE. The two hypocenter fault planes are NE-striking and NW-striking. The plane of NE direction is among N50°?70°E, the dip angles of fault planes are 60°?70° and it is very steep. The faultings of most earthquakes are dominantly characterized by dip-slip reverse and small part of faultings present strike-slip. The azimuths of principal compressive stress, the strikes of source fault planes and the dislocation types calculated from some small earthquakes before the 12 May 2008 Wenchuan earthquake are in accordance with that of the main shock. The average stress field of micro-rupture along the Longmenshan fault zone before the great earthquake is also consistent with that calculated from main shock. Zipingpu dam is located in the east side 20 km from the initial rupture area of the 12 May 2008 Wenchuan earthquake. The activity increment of small earthquakes in the Zipingpu dam is in the period of water discharging. The source parameter results of the small earthquakes which occurred near the initial rupture area of the 12 May 2008 Wenchuan earthquake indicate that the focal depths are 5 to 14 km and the source parameters are identical with that of earthquake. 相似文献
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汶川8.0级地震序列的小震震源机制及应力场特征 总被引：4，自引：1，他引：3
利用区域地震台网的数字地震波记录资料,由垂直向记录P和S振幅比值,结合部分清晰的P波初动记录资料,反演得到了2008年5月12日至2009年4月12日汶川8.0级地震序列中829个ML≥3.5的小震震源机制解。采用统计和力轴张量计算方法,分析了震源机制解参数并求取了余震区平均应力场。结果表明:用余震区北段小震震源机制解求得的节面为直立或倾斜,走向为NNE-SSW向,主压应力P轴方位为SWW-NEE方向,计算得到的平均应力张量σ1方向为77.1°;用余震区南段小震震源机制解求得的节面倾角较陡,在50°～90°之间,走向相对较分散,平均应力张量σ1方向为92.4°,呈EW向。从余震区南、北段的平均应力场方位随时间演化过程可以看出,余震区在2008年8月、9月、12月和2009年1月处于应力场调整阶段。最后研究了余震区南、北段的震源机制一致性参数θ及逆冲型地震类型随时间的变化,得到了一些有意义的结果。 相似文献
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The reason for the failure to forecast the Wenchuan M_S8.0 earthquake is under study, based on the systematically collection of the seismicity anomalies and their analysis results from annual earthquake tendency forecasts between the 2001 Western Kunlun Mountains Pass M_S8.1 earthquake and the 2008 Wenchuan M_S8.0 earthquake. The results show that the earthquake tendency estimation of Chinese Mainland is for strong earthquakes to occur in the active stage, and that there is still potential for the occurrence of a M_S8.0 large earthquake in Chinese Mainland after the 2001 Western Kunlun Mountains Pass earthquake. However the phenomena that many large earthquakes occurred around Chinese Mainland, and the 6-year long quietude of M_S7.0 earthquake and an obvious quietude of M_S5.0 and M_S6.0 earthquakes during 2002～2007 led to the distinctly lower forecast estimation of earthquake tendency in Chinese Mainland after 2006. The middle part in the north-south seismic belt has been designated a seismic risk area of strong earthquake in recent years, but, the estimation of the risk degree in Southwestern China is insufficient after the Ning’er M_S6.4 earthquake in Yunnan in 2007. There are no records of earthquakes with M_S≥7.0 in the Longmenshan fault, which is one of reasons that this fault was not considered a seismic risk area of strong earthquakes in recent years. 相似文献
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Zhiwei Zhang Wanzheng Cheng Xiang Ruan Peng Wu Lanzhou Institute of Seismology China Earthquake Administration Lanzhou China Earthquake Administration of Sichuan Province Chengdu China 《地震学报(英文版)》2009,(2):119-128
The seismicity of Longmenshan fault zone and its vicinities before the 12 May 2008 Wenchuan MS8.0 earthquake is studied.Based on the digital seismic waveform data observed from regional seismic networks and mobile stations, the focal mechanism solutions are determined.Our analysis results show that the seismicities of Longmenshan fault zone before the 12 May 2008 Wenchuan earthquake were in stable state.No obvious phenomena of seismic activity intensifying appeared.According to focal mechanism solutions of ... 相似文献
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为剖析2008年汶川MS8.0地震对后期地震的影响及发震区域构造应力场特征,首先利用2008年5月12日—2013年4月19日汶川地震及其邻区的1660条震源机制解,同时采用同一地震多个震源机制中心解的方法筛去重复地震事件的震源机制解,最终获得911个震源机制解。其次,通过网格搜索法分段反演出区域构造应力场。结果显示:东北区主要受WNW-ESE向的挤压,西南区受W-E向的挤压,中区受WSW-ENE向的挤压。西南到东北主压应力轴方向有所变化,这可能与龙门山地区受到来自印度板块北北东方向的俯冲推挤、四川盆地的阻挡和巴颜喀拉块体东南向挤压的联合作用有关。然后,基于USGS给出的汶川MS8.0地震的破裂模型,计算出该地震对附近强震的触发关系,结果表明,本次汶川地震对同属龙门山断裂西南端的芦山地震触发作用明显,对位于东昆仑断裂上的玛多地震也有一定的触发作用。最后,计算汶川MS8.0地震对周围断层的同震库仑应力变化,发现本次地震造成龙门山断裂南北两端、秦岭南缘断裂、鲜水河断裂东南端、东昆仑断裂、白玉断裂的库仑破裂应力增加,龙门山断裂南北两端和秦岭南缘断裂增加最为明显,对分析地震危险性有一定的参考意义。 相似文献
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Calculating the coseismic static Coulomb stress change induced by an earthquake and interseismic stress change permits to explain the distribution of aftershocks, the earthquake sequence and other seismic observations. Four earthquakes greater than M7 have occurred in the Longmenshan area before the 2013 Lushan earthquake since 1900. This paper analyzes the influence of these four events on the Lushan earthquake, the stress evolution after the Lushan earthquake accompany with strong earthquake sequence on Longmenshan Fault, and the stress state of the gap between the Lushan and Wenchuan earthquakes. To address these issues would help future seismic risk assessment in the region. We construct a three dimensional finite element model based on the geological structure, the deep inversion results of density and velocity, and the GPS and the stress observation data. The simulation results show that the annual variation rate of Coulomb stress is higher on the Xianshuihe fault and southern segment of the Longmenshan fault, which is consistant with the regional seismicity. The coseismic Coulomb stresses induced by Kangding, Songpan, and Wenchuan earthquakes at the Lushan earthquake epicenter is greater than 0, implying that the three earthquakes may promote the occurrence of the Lushan earthquake, especially the Wenchuan earthquake. The viscous relaxation is remarkable which cannot be ignored in the analysis of stress evolution. From the stress evolution of this area, we can find that the gap between the Wenchuan and Lushan earthquakes is still at a relatively high stress level after the Lushan earthquake. 相似文献
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FOCAL MECHANISM AND SEISMOGENIC STRUCTURE OF THE M5.0 YUEXI EARTHQUAKE ON 1 OCT. 2014, SOUTHWESTERN CHINA 下载免费PDF全文
下载免费PDF全文 The Oct.1,2014 M5.0 Yuexi earthquake occurred on the Daliang Shan fault zone where only several historical moderate earthquakes were recorded.Based on the waveform data from Sichuan regional seismic network,we calculated the focal mechanism solution and centroid depth of the M5.0 Yuexi earthquake by CAP (Cut and Paste) waveform inversion method,and preliminarily analyzed the seismogenic structure.We also calculated the apparent stress values of the M5.0 earthquake and other 14 ML≥4.0 events along the Shimian-Qiaojia fault segment of the eastern boundary of the Sichuan-Yunnan block.The result indicates that the parameters of the focal mechanism solution are with a strike of 256°,dip of 62°,and slip of 167° for the nodal plane Ⅰ,and strike of 352°,dip of 79°,and slip of 29° for the nodal plane Ⅱ.The azimuth of the P axis is 121° with dip angle of 11°,the azimuth of T axis is 217° with dip angle of 28°,and the centroid depth is about 11km,and moment magnitude is MW5.1.According to the focal mechanism solution and the fault geometry near the epicenter,we infer that the seismogenic fault is a branch fault,i.e.,the Puxiong Fault,along the central segment of the Daliang Shan fault zone.Thus,the nodal plane Ⅱ was interpreted as the coseismic rupture plane.The M5.0 Yuexi earthquake is a strike-slip faulting event with an oblique component.The above findings reveal the M5.0 Yuexi earthquake resulted from the left-lateral strike-slip faulting of the NNW Dalang Shan fault zone under the nearly horizontal principal compressive stress regime in an NWW-SEE direction.The apparent stress value of the Yuexi earthquake is 0.99MPa,higher than those of the ML ≥ 4.0 earthquakes along the eastern boundary of the Sichuan-Yunnan block since 2008 Wenchuan M8.0 earthquake,implying a relatively high stress level on the seismogenic area and greater potential for the moderate and strong earthquake occurrence.It may also reflect the current increasing stress level of the entire area along the eastern boundary,and therefore,posing the risk of strong earthquakes there. 相似文献