由Mw7.8昆仑山地震地表位错推断滑动位移

doi:10.7523/j.issn.2095-6134.2015.05.011

摘要/Abstract

摘要：

2001年M_W7.8昆仑山口西地震形成约400 km的地震破裂带,主震断层为一长度350 km、呈东西走向且近直立的走滑断层.主震断层附近的同震滑动位错为研究断层内部的力学性质及几何形态提供了重要参考.本文根据Freund的III-型位错模型,以实地测量和卫星测量的地表错动数据为约束条件,求取沿主震断层走向断层内部各点的滑动位移分布以及破裂面沿断层深度方向的扩展宽度.计算结果表明:III-型位错模拟结果所得断层面滑动位移分布特征和由有限断层模型体波反演得到的结果有较高的吻合程度,且在深度方向上呈现强烈的不均匀性.由III-型位错模型给出的断层内部的破裂宽度小于20 km,其平均值为8.4 km.进一步的对比分析表明:地表同震位移量的大小同断层的破裂宽度在尺度上存在明确的比例关系,沿断层走滑方向各点的滑动位移随深度的变化特征具有自相似性的分形特征.结合III-型位错模拟和体波反演结果,基于Andrews方法计算断层面上静态应力变化的分布,其分布特征同样具有很高的吻合度.

关键词: 昆仑山口西地震, 地表同震位移, 滑移模型, 断层面应力变化

Abstract:

The M_w7.8 Kunlunshan earthquake of November 14,2001, which ruptured over a total distance of about 400 km, was characterized by a 350-km-long main fault with an east-ward-propagating pulse of left-lateral slip. The field observations of coseismic displacement along the main fault provide us a good opportunity to study the earthquake source mechanism and fault geometry inside the earth. In this paper, based on Freund's III-dislocation model and constrained by two groups of surface rupture data from field investigation and geodetic measurement, we invert the slip distribution, the variation of static stress drop on the fault surface, and the fault width extending at depth along the fault strike-slip direction. The pattern of slip distribution on the fault surface deduced from the III-dislocation model is very similar to the result of the finite-fault solution based on the teleseismic body-wave inversion, showing that both slip distributions appear intensively heterogeneous in the special domain. The fault rupture width is much less than 20 km. These results also imply that the coseismic displacement along the fault strike direction on the earth surface is proportional to the fault width. In addition we also calculate the static stress change on the fault based on the III-dislocation model and slip distribution by teleseismic inversion. The analytical and numerical results show that they have high-level consistency.

Key words: Kunlunshan earthquake, surface coseismic displacement, slip model, stress change

中图分类号:

P315

米琦, 李彦恒, 申文豪, 史保平. 由M_w7.8昆仑山地震地表位错推断滑动位移[J]. 中国科学院大学学报, 2015, 32(5): 652-660.

MI Qi, LI Yanheng, SHEN Wenhao, SHI Baoping. Estimation of slip distribution for the M_w7.8 Kunlunshan earthquake by coseismic displacements[J]. , 2015, 32(5): 652-660.

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