伽师震源区中等强度地震矩张量反演及其应力场特征  

Moment inversion of moderate earthquakes and the locally perturbed stress field in the Jiashi source region

作　　者：赵翠萍[1] 陈章立[1] 郑斯华[1] 张智强[1] 

机构地区：[1]中国地震局地震预测研究所,北京100036

出　　处：《地球物理学报》2008年第3期782-792,共11页Chinese Journal of Geophysics

基　　金：中国地震局行业基金专项(20078-26)资助

摘　　要：使用区域数字地震台站记录的宽频带长周期波形资料,在时间域反演了1997～2004年伽师震源区52次中等强度地震的矩张量.反演结果揭示,在小尺度的伽师震源区内,震源机制解的P轴、T轴和N轴呈现出明显的分区特征.本文进一步把伽师震源区分为东区和西区,分别反演了东区与西区的应力场.应力场反演结果表明,东区的应力场主压应力轴走向为321°,基本水平.最大主张应力走向68°,倾角40°.截至2004年7月,伽师震源区西部的应力场一直较为稳定,最大主压应力方向为12°,最大主张应力方向282°,二者都基本水平,中等主应力轴基本直立.自西向东,伽师震源区最大主压应力轴逆时针旋转了49°,并且西区张应力的水平作用较为显著,东区压应力的水平作用显著.应力场的这种非均匀变化特征与GPS观测得到的地壳运动速率的空间分布以及塔里木盆地边界附近的地形地貌特征有很好的一致性.震源区深部结构的陡变以及位于震源区东部边界规模较大的NW走向的普昌断裂和色力布亚隐伏断裂可能对产生这种横向非均匀的局部应力场起了重要的作用.Moment tensors of 52 moderate earthquakes occurred in Jiashi source region, Xinjiang, from 1997 to 2004 were determined in time domain by using the long period waveforms recorded by regional broadband stations. The results demonstrate significant variations of the orientation and plunge of P, T and N axis from west to east. Therefore, we further divided the whole region into two parts, which are called the western part and the eastern part, and performed the stress tensor inversion respectively. The results show that in the eastern part, the maximum principal axis σ1 is almost horizontal and trends 321°, the minimum principal axis σ3 trends 68° with a plunge of 40°, and σ2 trends 213° with a plunge about 40°. Till 2004, the stress within the western part remained stable, with the σ1 and σ3 nearly horizontal and trending to 12° and 282° respectively, the middle axis σ2 almost vertical. Thus the maximum principal stress σ1 significantly rotates counterclockwise from N10°E in the west part to N39°W in the east part across the whole studied region. Compared with the stress field in the eastern part, the western part is under a stronger horizontal tension effect. This bilateral perturbation of stress field is consistent with the pattern of crustal deformation rate from GPS observation, as well as the topography map at the structure boundary between Tarim basin and Tienshan. We infer that both the sharp deformation in the deep crust and the large-scale NW-trending Puchang and Selibuya fault structures may play a crucial role in forming the local stress perturbation.

关 键 词：伽师震源区 中小地震 矩张量反演 应力场 

分 类 号：P315[天文地球—地震学] P542[天文地球—固体地球物理学]