Structure and seismogenic properties of the Mentawai segment of the Sumatra subduction zone revealed by local earthquake traveltime tomography
Structure and seismogenic properties of the Mentawai segment of the Sumatra subduction zone revealed by local earthquake traveltime tomography
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DOI：
10.1029/2011jb008469
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发表时间：
2012
影响因子：
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通讯作者：
R. Collings;D. Lange;A. Rietbrock;F. Tilmann;D. Natawidjaja;B. Suwargadi;Matthew Miller;J. Saul
中科院分区：
文献类型：
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作者：
R. Collings;D. Lange;A. Rietbrock;F. Tilmann;D. Natawidjaja;B. Suwargadi;Matthew Miller;J. Saul
2007年9月12日，苏门答腊俯冲带明打威段的南段发生了一次Mw8.4级地震，在那里，俯冲逆冲曾在1833年和1797年破裂。从2007年12月至2008年10月部署的临时当地地震台网获得的走时数据用于确定明打威段的二维（2-D）和三维（3-D）速度模型。地震活动分布显示沿俯冲界面和弧前盆地两侧上覆板块的两组内有明显的活动。下沉板块明显为高Vp （8.0 km/s）的倾斜区，可追溯至~ 50 km深度，岛屿下方和弧前盆地西侧Vp/Vs比值增大（1.75 ~ 1.90），表明存在水合洋壳。在板块上方，可以推断出深度小于30 km的浅层大陆莫霍线，表明大陆地幔与俯冲板块的交点远浅于孕震带的下倾极限，尽管在地幔楔脚处存在局部蛇纹岩化。外弧岛具有低Vp （4.5 ~ 5.8 km/s）和高Vp/Vs（大于2.0）的特征，为流体饱和沉积。外前弧的极低刚性导致了2010年10月25日明打威7.7级海啸地震的缓慢破裂。
[1] On 12 September 2007, an Mw8.4 earthquake occurred within the southern section of the Mentawai segment of the Sumatra subduction zone, where the subduction thrust had previously ruptured in 1833 and 1797. Traveltime data obtained from a temporary local seismic network, deployed between December 2007 and October 2008 to record the aftershocks of the 2007 event, was used to determine two-dimensional (2-D) and three-dimensional (3-D) velocity models of the Mentawai segment. The seismicity distribution reveals significant activity along the subduction interface and within two clusters in the overriding plate either side of the forearc basin. The downgoing slab is clearly distinguished by a dipping region of highVp (8.0 km/s), which can be a traced to ∼50 km depth, with an increased Vp/Vs ratio (1.75 to 1.90) beneath the islands and the western side of the forearc basin, suggesting hydrated oceanic crust. Above the slab, a shallow continental Moho of less than 30 km depth can be inferred, suggesting that the intersection of the continental mantle with the subducting slab is much shallower than the downdip limit of the seismogenic zone despite localized serpentinization being present at the toe of the mantle wedge. The outer arc islands are characterized by low Vp (4.5–5.8 km/s) and high Vp/Vs (greater than 2.0), suggesting that they consist of fluid saturated sediments. The very low rigidity of the outer forearc contributed to the slow rupture of the Mw 7.7 Mentawai tsunami earthquake on 25 October 2010.