The Updip Seismic/Aseismic Transition of the Sumatra Megathrust
The Updip Seismic/Aseismic Transition of the Sumatra Megathrust
复制标题
苏门答腊巨型逆冲断层的上倾地震/抗震转变
DOI：
10.1111/j.1365-246x.2010.04597.x
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发表时间：
2010
影响因子：
18.3
通讯作者：
D. Natawidjaja
中科院分区：
文献类型：
--
作者：
F. Tilmann;Tom Craig;I. Grevemeyer;B. Suwargadi;H. Kopp;E. Flueh;R. Collings;D. Lange;D. Natawidjaja
大俯冲地震在单个事件的破裂和边缘的长期历史中都表现出分段性。2004年12月26日亚齐-安达曼和2005年3月28日苏门答腊岛北方的尼亚斯地震是近年来最大的两次地震，同震和震后位移都受到前所未有的详细限制。使用余震的位置从一个临时的地震台阵在边界区域之间的事件和波形建模的大余震，我们证明了绝大多数的余震在研究区域发生在板块界面上的一个狭窄的带（20公里）向海的外弧高。比较地震活动性分布与同震和震后位移，我们推断地震带标志着孕震区和稳定滑动之间的过渡。该带的位置以及由此产生的过渡似乎与1000米水深等值线相关。这种密切的对应关系在两次大地震之间的边界处被破坏，在那里，向孕震行为的转变发生在向陆地方向进一步延伸1.25公里的地方。在Simeulue以西，整个前弧的海底测深深度超过500米，地震带突然终止，余震活动的焦点在海沟附近。后滑的地震效率沿沿着变化很大：Banyak群岛以下的部分，在尼亚斯地震的两个主要凹凸体之间的差距，容纳了更大比例的后滑地震。
Great subduction earthquakes exhibit segmentation both within the rupture of individual events and in the long term history of the margin. The 2004 December 26 Aceh-Andaman and 2005 March 28 Nias event in northern Sumatra are two of the largest earthquakes in recent years, with both co- and post-seismic displacements constrained in unprecedented detail. Using aftershock locations from a temporary seismic array in the boundary region between both events and waveform modelling of large aftershocks, we demonstrate that the vast majority of aftershocks in the study region occur on the plate interface within a narrow band ( 20 km) seaward of the outer arc high. Comparing the seismicity distribution to the co- and post-seismic displacements, we infer that the seismic band marks the transition between the seismogenic zone and stable sliding. The location of the band and therefore the transition appears to be correlated with the ∼500 m bathymetry contour. This close correspondence is disrupted at the boundary between the two great earthquakes, where the transition to seismogenic behaviour occurs further landward by ∼25 km. To the west of Simeulue, where seafloor bathymetry throughout the forearc is deeper than 500 m, the seismic band terminates abruptly and the focus of aftershock activity is found near the trench. The seismic efficiency of afterslip varies dramatically along strike: the segment below the Banyak islands, in the gap between the two main asperities of the Nias earthquake, accommodates a much larger proportion of afterslip seismically.