The 2013, Mw 7.7 Balochistan earthquake, energetic strike-slip reactivation of a thrust fault
The 2013, Mw 7.7 Balochistan earthquake, energetic strike-slip reactivation of a thrust fault
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DOI：
10.1016/j.epsl.2014.01.036
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发表时间：
2014-04-01
影响因子：
5.3
通讯作者：
Helmberger, Don
中科院分区：
文献类型：
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作者：
Avouac, Jean-Philippe;Ayoub, Francois;Helmberger, Don
我们根据 Landsat-8 图像的亚像素相关测量的地表形变，结合远震波形的反投影和有限源建模，分析了 2013 年 9 月 24 日俾路支省 7.7 级地震。地震在查曼走滑断层以南成核，并沿着凯赫带前部的霍沙布断层向西南传播。破裂多为单侧，平均扩展速度为 3 km/s，产生 200 km 的地表断层迹，纯走滑位移峰值可达 10 m，平均约为 6 m。有限源模型显示滑移在表面附近最大。尽管 Hoshab 断层向北倾斜 45°，但根据其起源为莫克兰增生棱柱内的逆冲断层，该地震期间的滑动几乎完全是走滑。这种非最佳定向断层上的大地震滑移可能由于自由表面对动态应力的影响或断层带的特殊性质而导致强烈的动态弱化而增强。莫克兰东部逆冲断层上的走滑断层被解释为由于增生棱柱在印度板块上隆起时向东挤压所致。这次地震使莫克兰巨型逆冲断层的部分区域、基尔塔尔山脉的一些逆冲断层以及查曼断层系内的走滑断层更接近断裂。余震集中在震中以北的查曼断层系内，与破裂传播的方向相反。相比之下，在最大力矩释放区域检测到的余震很少。在这个例子中，余震不能用来推断地震特征。 (C) 2014 Elsevier B.V. 保留所有权利。
We analyse the Mw 7.7 Balochistan earthquake of 09/24/2013 based on ground surface deformation measured from sub-pixel correlation of Landsat-8 images, combined with back-projection and finite source modeling of teleseismic waveforms. The earthquake nucleated south of the Chaman strike-slip fault and propagated southwestward along the Hoshab fault at the front of the Kech Band. The rupture was mostly unilateral, propagated at 3 km/s on average and produced a 200 km surface fault trace with purely strike-slip displacement peaking to 10 m and averaging around 6 m. The finite source model shows that slip was maximum near the surface. Although the Hoshab fault is dipping by 45 to the North, in accordance with its origin as a thrust fault within the Makran accretionary prism, slip was nearly purely strike-slip during that earthquake. Large seismic slip on such a non-optimally oriented fault was enhanced possibly due to the influence of the free surface on dynamic stresses or to particular properties of the fault zone allowing for strong dynamic weakening. Strike-slip faulting on thrust fault within the eastern Makran is interpreted as due to eastward extrusion of the accretionary prism as it bulges out over the Indian plate. Portions of the Makran megathrust, some thrust faults in the Kirthar range and strike-slip faults within the Chaman fault system have been brought closer to failure by this earthquake. Aftershocks cluster within the Chaman fault system north of the epicenter, opposite to the direction of rupture propagation. By contrast, few aftershocks were detected in the area of maximum moment release. In this example, aftershocks cannot be used to infer earthquake characteristics. (C) 2014 Elsevier B.V. All rights reserved.