Splay faults imaged by fluid-driven aftershocks of the 2004 Mw 9.2 Sumatra-Andaman earthquake
Splay faults imaged by fluid-driven aftershocks of the 2004 Mw 9.2 Sumatra-Andaman earthquake
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2004 年 Mw 9.2 苏门答腊-安达曼地震流体驱动余震拍摄的张开断层
作者：
F. Waldhauser;D. Schaff;T. Diehl;E. Engdahl
2004年苏门答腊-安达曼9.2级地震余震的高精度远震双差定位和震源机制揭示了苏门答腊北部近海增生棱镜中一个活跃的叠瓦状断裂系统。它们揭示了在大逆冲断层上方一个向东北倾斜的浅层逆冲断层的反复断裂，我们将其解释为一个从大逆冲断层上升到约55公里深并穿过上覆的巽他板块的展斜断层的重新激活。在亚齐盆地西部的地震后测深数据中，预计的展断层与海底的相交与最近活跃的逆冲断层相关。对条纹状余震分布的时空分析表明，从俯冲洋壳释放的上升流体沿着继承的海底构造可能控制上覆板块的脆性断裂。我们推测，如果展断层在同震上是活跃的，那么它可能会导致前弧脊的垂直隆升放大，并在2004年破裂后产生了袭击苏门答腊岛西北海岸的灾难性近场海啸。
High-precision teleseismic double-difference locations and focal mechanisms of aftershocks of the A.D. 2004 M w 9.2 Sumatra-Andaman earthquake illuminate an active imbricate fault system in the accretionary prism offshore northern Sumatra. They reveal repeated failure of a shallow northeast-dipping thrust fault above the megathrust, which we interpret to be the reactivation of a splay fault that rises from the megathrust at ∼55 km depth and cuts through the overriding Sunda plate. The projected intersection of the splay fault with the seafloor correlates with a recently active thrust fault seen in postseismic bathymetry data west of the Aceh basin. A spatiotemporal analysis of the streaky aftershock distribution indicates that ascending fluids released from the subducting oceanic crust along inherited seafloor fabric may control brittle fracture in the overriding plate. We speculate that if the splay fault was active coseismically, it may have led to amplified vertical uplift of the forearc ridge and contributed to generating the cataclysmic near-field tsunami that struck the northwest Sumatra coast following the 2004 rupture.