To investigate the mechanism of tectonic tremor and the factors that influence its occurrence and fluctuations, we use seismic reflection data to map in detail a shear zone associated with the plate boundary fault in the Nankai accretionary prism, southwest Japan. The shear zone can be identified from its low seismic velocity and low reflection amplitude, which may signify the presence of high pore pressure, around the transition boundary from frontal outer wedge to inner wedge. A detailed comparison of the mapped shear zone and the distribution of tectonic tremor demonstrate that tremor tended to occur in the thick part of the shear zone, where high pore fluid pressure may weaken faults and thereby facilitate slow earthquakes. Furthermore tremors align on the oblique strike-slip faults that caused variation of the shear zone thickness as well as fluctuation of stress and pore pressure. The oblique strike-slip faults that control the thickness of the shear zone and tremor distributions are interpreted as features formed by the collision of an accretionary prism against a landward tectonic backstop.

中文翻译：

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剪切带厚度和走滑断裂对日本西南部南海海槽构造震动的影响

为了研究构造震动的机制以及影响其发生和波动的因素，我们利用地震反射数据详细绘制了日本西南部南海增生棱柱中与板块边界断层相关的剪切带。剪切带可以通过其低地震速度和低反射幅度来识别，这可能意味着在从锋面外楔到内楔的过渡边界周围存在高孔隙压力。对绘制的剪切带和构造震动分布的详细比较表明，震动往往发生在剪切带的较厚部分，那里的高孔隙流体压力可能会削弱断层，从而促进慢地震的发生。此外，斜走滑断层上的震动会引起剪切带厚度的变化以及应力和孔隙压力的波动。控制剪切带厚度和震颤分布的斜走滑断层被解释为增生棱柱体与向陆构造逆止器碰撞而形成的特征。