Geometry and slip rates of active blind thrusts in a reactivated back-arc rift using shallow seismic imaging: Toyama basin, central Japan
Geometry and slip rates of active blind thrusts in a reactivated back-arc rift using shallow seismic imaging: Toyama basin, central Japan
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DOI：
10.1016/j.tecto.2017.08.002
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发表时间：
2017-10
期刊：
影响因子：
2.9
通讯作者：
T. Ishiyama;N. Kato;Hiroshi P. Sato;S. Koshiya;Shigeru Toda;Kenta Kobayashi
中科院分区：
文献类型：
--
作者：
T. Ishiyama;N. Kato;Hiroshi P. Sato;S. Koshiya;Shigeru Toda;Kenta Kobayashi
在城市化地区，活动的盲冲断层可能是一种主要的地震灾害，通常很难用地震反射测量进行成像。为了解决沿海平原的这些挑战，我们收集了大约8公里长的陆上高分辨率二维(2D)地震反射数据，使用800个地震检波器的密集阵列，穿过位于日本海富山海槽西南延伸的故障裂谷系统内被挤压重新激活的正断层。对地震反射数据的处理揭示了它们详细的地下结构，深度约为3公里。解释的深度转换剖面与附近的新近系地层对比，表明了以前未被识别的复杂逆冲构造的存在及其沿走向的变化，该构造由前缘内的活动断层-弯曲褶皱和一对弯曲滑动断层组成，以及新发现的冲积平原下方的前缘活动盲冲断层。此外，下部至上更新世单元变形的生长地层和褶皱陡坎记录了其构造生长和断裂活动的近代历史。这一实例表明，用密集分布的地震记录仪进行浅层地震反射成像是一种有用的工具，可以用来确定活动的盲冲断层的位置、最近的断层活动和复杂的几何形状。
Active blind thrust faults, which can be a major seismic hazard in urbanized areas, are commonly difficult to image with seismic reflection surveys. To address these challenges in coastal plains, we collected about 8 km-long onshore high-resolution two-dimensional (2D) seismic reflection data using a dense array of 800 geophones across compressionally reactivated normal faults within a failed rift system located along the southwestern extension of the Toyama trough in the Sea of Japan. The processing of the seismic reflection data illuminated their detailed subsurface structures to depths of about 3 km. The interpreted depth-converted section, correlated with nearby Neogene stratigraphy, indicated the presence of and along-strike variation of previously unrecognized complex thrust-related structures composed of active fault-bend folds coupled with pairs of flexural slip faults within the forelimb and newly identified frontal active blind thrusts beneath the alluvial plain. In addition, growth strata and fold scarps that deform lower to upper Pleistocene units record the recent history of their structural growth and fault activity. This case shows that shallow seismic reflection imaging with densely spaced seismic recorders is a useful tool in defining locations, recent fault activity, and complex geometry of otherwise inaccessible active blind thrust faults.