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新疆伽师强震群区三维地壳上地幔S波速度结构及其地震成因的探讨
引用本文:刘启元,陈九辉,李顺成,郭飚.新疆伽师强震群区三维地壳上地幔S波速度结构及其地震成因的探讨[J].地球物理学报,2000,43(3):356-365.
作者姓名:刘启元  陈九辉  李顺成  郭飚
作者单位:中国地震局地质研究所,北京100029
基金项目:国家自然科学基金,国家科技部和地震科学联合基金!49834005,中国地震局地质研究所论著!2000B0009
摘    要:1997年1月21日至4月16日(北京时间)新疆伽师地区连续发生了7次6级以上 强烈地震.为了深入研究该强震群形成的构造背景,我们在伽师强震群区及其邻域大约 11 000km的范围内布设了由 30台宽频带数字地震仪组成的流动地震台阵,台站的间距约5- 10km.利用远震体波接收函数的叠加偏移分析及其非线性反演技术,研究了台阵下方0- 100km深度范围内地壳、上地幔的三维S波速度结构.结果表明:1)Moho界面的深度在塔里 木盆地一侧为40-52km,而在靠近天山一侧的褶皱变形区为60-76km,南天山山前折皱变形 区的地壳厚度明显增大,地壳内部产生了明显变形;2)塔里木盆地北缘存在明显的不均匀性, 塔里木盆地与天山之间的接触变形关系显示了塔里木盆地向北北西方向的挤压作用,台阵下 方壳幔界面的地形与地表的地貌特征有较好的相关性,山前弧形褶皱带的形成与地下深部结 构及挤压作用有关;3)伽师强震群分布在壳幔界面梯度带的上方,该震群的成因可能与震源 区附近的隐伏断裂活动有关;4)由于震源处于褶皱变形区的地壳上部,相应的剪切模量较小, 这可能是伽师强震群应力降明显偏低的...

关 键 词:流动地震台  阵伽师强震群  地壳上地幔结构  天山动力学  
文章编号:0001-5733(2000)03-0356-10
收稿时间:1999-09-21
修稿时间:1999年9月21日

PASSIVE SEISMIC EXPERIMENT IN XINGJIANG-JIASHI STRONG EARTHQUAKE REGION AND DISCUSSION ON ITS SEISMIC GENESIS
LIU QI-Yuan,CHEN JIUHUI,LI SHUN-CHENG,GUO BIAO.PASSIVE SEISMIC EXPERIMENT IN XINGJIANG-JIASHI STRONG EARTHQUAKE REGION AND DISCUSSION ON ITS SEISMIC GENESIS[J].Chinese Journal of Geophysics,2000,43(3):356-365.
Authors:LIU QI-Yuan  CHEN JIUHUI  LI SHUN-CHENG  GUO BIAO
Institution:Institute of Geology, China Seismological Bureau, Beijing 100029, China
Abstract:From January 21 to April 16 of 1997, seven strong earthquakes took place in Jiashi region of Xinjiang, China. This Phenomenon was never happened in Chinese continent since earthquakes were able to be recorded by instruments. To investigate the deep structure environment of the Jiashi strong earthquake sequence, a portable broadband seismic array of 30 stations was set up in Jiashi region over about 11,000 km2. The portable array crossed the Tarim basin and the Tian Shan fold belt. The distance between stations is about 5-10 km. The frequency bandwidth of our observation system is 0.05--20 Hz. The 3--D S-wave velocity structure down to 100 km beneath the army was obtained by using the teleseismic receiver function migration and its nonlinear inversion techniques (Liu etc. 1996). The following conclusions can be obtained from our observations: l) The Moho depth is about 4052 kin on the side of the Tarim basin and becomes 60-76 km deep on the side close to the Tien Shan. The crustal thickness beneath the fold belt nearby the south Tien Shan is much thicker than that of the Tarim basin and the obvious tectonic deformation exists in the crust. 2) The north boundary of the Tarim basin is clearly laterally inhomogeneous. The relationship of the contact deformation between Tarim and Tien Shan reveals the compressional movement to the NNW direction. The topography of the Moho discontinuity beneath our array has obvious correlation with the arctuate tectonics on the surface. The arctuate fold formation is closely related with the deep structure and the compression by the Tarim basin. 3) The Jiashi strong earthquake sequence mainly occurred over the gradient zone of the crust--mantle boundary. The genesis of the Jiashi earthquake sequence probably related to the activity of the conceal faults nearby the sources. This may result from the inhomogeneous deformation at the north boundary and the current tectonic movement of the Tarim basin. 4) The Jiashi strong earthquake sequence mainly occurred in the upper crust beneath the fold belt with a lower shear module. This could be a reason why the stress drop of these events is much smaller than common. All of these demonstrate that the Jiashi earthquake sequence genesis is related not only to the current tectonic movement of the Tarim basin, but also to the deep structure. This will need to be investigated further by the numerical stress modeling.
Keywords:Passive seismic experiment Jiashi strong earthquake sequence  Crustal and upper mantle structure  Tian Shan dynamics  
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