The structure of the Sumatran Fault revealed by local seismicity
The structure of the Sumatran Fault revealed by local seismicity
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DOI：
10.1029/2011gl050440
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发表时间：
2012-01
影响因子：
5.2
通讯作者：
O. Weller;D. Lange;F. Tilmann;D. Natawidjaja;A. Rietbrock;R. Collings;L. Gregory
中科院分区：
文献类型：
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作者：
O. Weller;D. Lange;F. Tilmann;D. Natawidjaja;A. Rietbrock;R. Collings;L. Gregory
Sunda巨型逆冲断层和（走滑）Summandra断层（SF）的组合代表了滑动划分的典型例子。然而，叠加在SF上的是破坏局部应变场的几何不规则性。最大的这样的特征是在苏门答腊中部，SF分裂成两个断层链，相距35公里。沿该分叉处沿着350公里的区域安装了密集的局部网络，记录了2008年4月至2009年2月期间的1 016次地壳事件。其中528个事件，震级在1.1到6.0之间，使用双差相对定位方法进行定位。这些相对震源位置揭示了SF地壳结构的一些新特征。在分叉的西北和东南部，SF只有一个断层链，地震活动强烈集中在地表迹线以下，表明垂直断层在15km深的地方发震。相反，在分叉处观察到强烈的地震活动，在平面和横截面上显示条纹，表明分叉处有一个复杂的断层系统。结合地形地貌和震源机制分析，提出该分叉是一个走滑复式系统，两条主断裂分支之间存在复杂的断裂活动。
The combination of the Sunda megathrust and the (strike‐slip) Sumatran Fault (SF) represents a type example of slip‐partitioning. However, superimposed on the SF are geometrical irregularities that disrupt the local strain field. The largest such feature is in central Sumatra where the SF splits into two fault strands up to 35 km apart. A dense local network was installed along a 350 km section around this bifurcation, registering 1016 crustal events between April 2008 and February 2009. 528 of these events, with magnitudes between 1.1 and 6.0, were located using the double‐difference relative location method. These relative hypocentre locations reveal several new features about the crustal structure of the SF. Northwest and southeast of the bifurcation, where the SF has only one fault strand, seismicity is strongly focused below the surface trace, indicating a vertical fault that is seismogenic to ∼15 km depth. By contrast intense seismicity is observed within the bifurcation, displaying streaks in plan and cross‐section that indicate a complex system of faults bisecting the bifurcation. In combination with analysis of topography and focal mechanisms, we propose that the bifurcation is a strike‐slip duplex system with complex faulting between the two main fault branches.