Episodic subsidence and active deformation of the forearc slope along the Japan Trench near the epicenter of the 2011 Tohoku Earthquake
Episodic subsidence and active deformation of the forearc slope along the Japan Trench near the epicenter of the 2011 Tohoku Earthquake
复制标题
DOI：
10.1016/j.epsl.2014.09.048
复制
发表时间：
2014-12-15
影响因子：
5.3
通讯作者：
Sasaki, Tomoyuki
中科院分区：
文献类型：
--
作者：
Arai, Kohsaku;Inoue, Takahiko;Sasaki, Tomoyuki
为了调查日本东北太平洋沿岸的现代地质变形，我们在2007年获得了高分辨率的多道地震反射和测深数据。研究区域位于日本海沟沿着，靠近2011年东北太平洋沿岸地震的震中。地震剖面没有显示出弧前斜坡上的活动构造指示挤压应力。相反，最近的构造变形的特点是伸展沉降和正断层的发生在斜坡上的一系列小盆地的水深为3000米。这些孤立的盆地是最厚的（类似于525米，类似于0.7秒的双向旅行时间）在平坦的水深测量区域的基础区域。孤立盆地的宽度范围从几公里到40公里，覆盖着分层沉积物上重叠在终端的凹下反射。盆地下方的地震单元显示出连续的、近平行的内部反射体，这表明与沉降有关的变形是最近突然开始的。在上斜坡区，白垩系顶部不整合面上的沉积物厚度基本不变。然而，局部出现透镜状内反射图案。透镜状沉积单元的宽度和内反射模式与孤立盆地相似。我们推断，上覆板块的伸展变形，在孤立的盆地的形式，发生在地质时间。我们认为，弧前斜坡沿着日本海沟的地质结构是典型的俯冲侵蚀，并提出幕式沉降伴随着正常断层是最近的变形。(C)2014爱思唯尔有限公司版权所有。
To investigate the present-day geological deformation occurring off the Pacific coast of Tohoku, Japan, we obtained high-resolution multichannel seismic reflection and bathymetric data in 2007. The study area is located along the Japan Trench near the epicenter of the 2011 off the Pacific coast of Tohoku Earthquake. The seismic profiles do not show active structures indicative of compressional stress on the forearc slope. Instead, recent tectonic deformation is characterized by extensional subsidence and the occurrence of normal faults within a series of small basins on the slope to a water depth of 3000 m. These isolated basins are thickest (similar to 525 m, similar to 0.7 s two-way travel time) in regions underlying areas of flat bathymetry. The isolated basins range in width from several to 40 km and are covered by stratified sediments onlapping at the termination of concave-down reflectors. The seismic units below the basins show continuous, subparallel internal reflectors, suggesting that the subsidence-related deformation started abruptly and recently. The thickness of sediments overlying the unconformity at the top of the Cretaceous is roughly constant in the upper slope area. However, lenticular internal reflection patterns occur locally. The lenticular sedimentary units are similar to the isolated basins in terms of their widths and internal reflection patterns. We infer that episodes of extensional deformation of the overriding plate, in the form of isolated basins, have occurred over geological time. We suggest that the geological structures of the forearc slope along the Japan Trench are typical of those resulting from subduction erosion and propose that the episodic subsidence accompanied by normal faulting is the most recent deformation. (C) 2014 Elsevier B.V. All rights reserved.