Evolution of the Nankai Trough décollement from the trench into the seismogenic zone: Inferences from three-dimensional seismic reflection imaging
Evolution of the Nankai Trough décollement from the trench into the seismogenic zone: Inferences from three-dimensional seismic reflection imaging
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DOI：
10.1130/g20211.2
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发表时间：
2004-04
期刊：
影响因子：
5.8
通讯作者：
N. Bangs;T. Shipley;S. Gulick;G. Moore;Shinichi Kuromoto;Y. Nakamura
中科院分区：
文献类型：
--
作者：
N. Bangs;T. Shipley;S. Gulick;G. Moore;Shinichi Kuromoto;Y. Nakamura
利用三维地震反射资料，绘制了南海海槽俯冲逆冲断层从海沟到孕震区的地震反射振幅图。滑脱逆冲断层形成于岩性均一的四国盆地下部相内，沿着最初无反射界面。由于增生楔形固结以及俯冲剖面的快速加载和延迟固结，该反射是从增生和俯冲沉积物质之间的孔隙度对比发展而来的。一幅下沉幅度图显示，从海沟的高幅度到向陆地方向25-30公里处几乎检测不到的幅度有了明显的下降。其他三个观测结果与振幅下降相吻合：（1）滑脱最初下降到更深的地层水平，（2）楔形锥急剧增加，（3）逆冲断层成为地震。振幅下降和同时发生的滑脱和增生楔构造与孕震行为是由于流体的损失和潜在的过剩流体压力沿俯冲逆冲带向下沿着损失。
We mapped the amplitude of the Nankai Trough subduction thrust seismic reflection from the trench into the seismogenic zone with three-dimensional seismic reflection data. The decollement thrust forms within the lithologically homogeneous Lower Shikoku Basin facies along an initially nonreflective interface. The reflection develops from a porosity contrast between accreted and underthrust sedimentary material because of accretionary wedge consolidation and rapid loading and delayed consolidation of the underthrust section. A decollement-amplitude map shows a significant decline from high amplitudes at the trench to barely detectable levels 25–30 km landward. Three other observations coincide with the amplitude decline: (1) the decollement initially steps down to deeper stratigraphic levels, (2) the wedge taper increases dramatically, and (3) the thrust becomes seismogenic. The amplitude decline and the coincident decollement and accretionary- wedge tectonic and seismogenic behavior are attributed to the loss of fluids and potentially loss of excess fluid pressures downdip along the subduction thrust.