Strength characteristics of Japan Trench borehole samples in the high-slip region of the 2011 Tohoku-Oki earthquake
Strength characteristics of Japan Trench borehole samples in the high-slip region of the 2011 Tohoku-Oki earthquake
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DOI：
10.1016/j.epsl.2014.12.014
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发表时间：
2015-02-15
影响因子：
5.3
通讯作者：
Kopf, Achim J.
中科院分区：
文献类型：
--
作者：
Ikari, Matt J.;Kameda, Jun;Kopf, Achim J.
2011年东北-冲地震表明，板块边界俯冲巨型逆冲断层的最浅区域可以承载大量的同震滑动，产生大的破坏性海啸，这与通常的假设相反，即深度小于5公里的松散粘土丰富的沉积物的摩擦特性应该抑制破裂。我们报告在低滑动速度（类似于0.5）的实验室剪切实验。由于蒙皂石粘土含量升高，断层较弱，与成分相似的远洋粘土层非常相似。完整的围岩样品的较高的凝聚力加上其较高的无定形二氧化硅含量表明，由于成岩胶结作用和低粘土含量，围岩较强。我们的测量结果还表明，在断层带中的强烈发展的原地织物并不有助于其摩擦弱点，但导致一个近cohesionless断层带，这可能有利于破裂传播，通过降低剪切强度和表面能在破裂前端的尖端。我们认为，2011年东北地震期间的浅破裂和大的同震滑动是由一个弱的和无粘性的断层与强围岩相结合，驱动局部变形在一个狭窄的区域内。(C)2014爱思唯尔有限公司版权所有。
The 2011 Tohoku-Oki earthquake demonstrated that the shallowest reaches of plate boundary subduction megathrusts can host substantial coseismic slip that generates large and destructive tsunamis, contrary to the common assumption that the frictional properties of unconsolidated clay-rich sediments at depths less than similar to 5 km should inhibit rupture. We report on laboratory shearing experiments at low sliding velocities ( similar to 0.5). The fault is weak due to elevated smectite clay content and is frictionally similar to a pelagic clay layer of similar composition. The higher cohesion of intact wall rock samples coupled with their higher amorphous silica content suggests that the wall rock is stronger due to diagenetic cementation and low clay content. Our measurements also show that the strongly developed in-situ fabric in the fault zone does not contribute to its frictional weakness, but does lead to a near-cohesionless fault zone, which may facilitate rupture propagation by reducing shear strength and surface energy at the tip of the rupture front. We suggest that the shallow rupture and large coseismic slip during the 2011 Tohoku earthquake was facilitated by a weak and cohesionless fault combined with strong wall rocks that drive localized deformation within a narrow zone. (C) 2014 Elsevier B.V. All rights reserved.