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Simple flow models of accretionary prisms: Predictions for coexisting arc-normal compression and extension, and implications for locked zones on the interplate megathrust

机译：增生棱镜的简单流动模型：弧线法向压缩和扩展共存的预测，以及板间超推力锁定区域的含义

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摘要

In accretionary prisms formed in subduction zones, accreted sediments deform due to the drag of the subducting plate, resulting in arc-normal compression. In the Cascadia and eastern Nankai subduction zones, however, arc-parallel normal faults, which indicate the occurrence of arc-normal extension, have been observed at the rear of the accretionary prisms. In this study, the deformation caused by the subducting plate in the accretionary prism is calculated using a simple fluid model that considers temperature-dependent rheology. The qualitative results show that a circulating flow is induced by the subducting plate under a lid formed at the rear of the accretionary prisms at higher temperatures, while, in lower-temperature prisms, the flow pattern is analogous to a simple corner flow, and the circulating flow is not induced. Prism materials flow trenchward just under the lid, and this return flow may be the cause of the arc-normal extension observed in the accretionary prisms. Most of the subduction velocity is accommodated by ductile deformation at the rear of the accretionary prisms, resulting in lower seismic coupling at the deeper interplate megathrusts. In the frontal part of the accretionary prisms, where imbricate thrusts develop, low rigidity due to high porosity and pore fluid pressure in the compacting sediment, together with higher concentrations of clay minerals with low frictional coefficients, probably prevents seismic slip at the interplate megathrusts. Locked zones develop between the extensional and imbricate thrust regions in the subduction zones. For low-temperature prisms, locked zones are located arc side of the imbricate thrust region. The fore-arc basin is thus formed above the locked zone in accretionary prisms. In the eastern Nankai subduction zone, another locked zone is estimated to be located in the lower crust. The location of the arc side of the imbricate thrust region in the western and central Nankai subduction zones may be controlled by the thrust intersection with the top of the lower crust and the splay-fault, respectively.
机译：在俯冲带上形成的增生棱柱中，由于俯冲板的阻力，积聚的沉积物会变形，从而导致圆弧法向压缩。然而，在卡斯卡迪亚和南海俯冲带东部，在增生棱镜的后部观察到弧平行的正断层，表明弧的正延伸。在这项研究中，使用简单的考虑温度依赖性流变的流体模型计算了增生棱镜中俯冲板引起的变形。定性结果表明，在较高温度下，消减板在增生棱镜后部形成的盖子下面的导流板中引起循环流，而在较低温度的棱镜中，流型类似于简单的角流，并且不会引起循环流。棱镜材料正好在盖子下面向沟槽流动，并且这种回流可能是在增生棱镜中观察到的法线延伸的原因。俯冲速度的大部分由增生棱镜后部的延性变形提供，从而在较深的板间巨推力处产生较低的地震耦合。在增生棱柱的前部，发育有岩性推力，由于高孔隙率和压实沉积物中的孔隙流体压力而导致的低刚度，以及较高浓度的低摩擦系数的粘土矿物，很可能防止了板间大推力的地震滑动。在俯冲带的伸展和thrust回推力区之间会形成锁定区。对于低温棱镜，锁定区域位于波纹状推力区域的弧形侧。因此，弧形前盆形成在附加棱镜的锁定区域上方。在南开俯冲带东部，估计另一个锁带位于地壳下部。南海俯冲带西部和中部的盘状冲断带弧面侧的位置可以分别由与下地壳顶部和张开断层的冲断相交控制。

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    Furukawa Y.;

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  • 年度 2011
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  • 正文语种 eng
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