Propagation of a precursory detachment front along a seismogenic plate interface in a rate-state model of earthquake cycles
Propagation of a precursory detachment front along a seismogenic plate interface in a rate-state model of earthquake cycles
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地震周期速率状态模型中前兆脱离锋沿发震板块界面的传播
DOI：
10.1093/gji/ggab331
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发表时间：
2022
影响因子：
2.8
通讯作者：
N.
中科院分区：
文献类型：
--
作者：
Kato;N.
利用速率和状态相关的摩擦定律，对板块界面俯冲带的地震周期进行了数值模拟，以检查地震滑动过程传播到锁定板块界面。该模型假定在二维均匀弹性半空间中存在逆断层，并以等速施加相对板块运动。模拟地震在发震板块界面浅层反复发生，具有速度减弱的摩擦特性，而在发震板块界面深层发生稳定滑动，具有速度增强的摩擦特性。在震间期，深部稳定滑动使剪切应力集中在锁定板块界面的较深边缘，应力发生局部下降，导致板块分离。由此产生的分离锋面沿着发震板块界面向上传播，直到地震发生，引起地震滑动，其滑动速度明显低于施加的相对板块速度。在每种情况下，分离锋面的传播速度几乎是恒定的，它与相对板块速度成正比，与有效正应力成反比。滑移速度增加的偶发性事件发生在震间期的后半段，此时特征滑移距离较小。幕式滑动的上倾传播受到低应力屏障的抑制，而幕式滑动向下反向传播。在模拟周期的最后几年，平均滑动速度与大板块间地震发生的时间近似成反比。
A numerical simulation of earthquake cycles at the subduction zone of a plate interface was conducted, using a rate- and state-dependent friction law, to examine aseismic sliding processes propagating into a locked plate interface. In the model, a reverse fault is assumed in a 2-D uniform elastic half-space, and relative plate motion is imposed with a constant velocity. Simulated earthquakes occur repeatedly at a shallower seismogenic plate interface with a velocity-weakening frictional property, while stable sliding occurs in the deeper part, in which a velocity-strengthening frictional property is assumed. During interseismic periods, deep stable sliding causes shear stress to concentrate at the deeper edge of the locked plate interface, and a partial drop in stress occurs, resulting in plate detachment. The resulting detachment front propagates upwards along the seismogenic plate interface until an earthquake occurs, causing aseismic sliding with a sliding velocity significantly lower than the imposed relative plate velocity. The propagation velocity of the detachment front is almost constant in each case, and it is proportional to the relative plate velocity and inversely proportional to the effective normal stress. Episodic events of increased slip velocity occur in the latter half of an interseismic period when the characteristic slip distance is small. Updip propagation of episodic slip is arrested by a low stress barrier, and episodic slips backpropagate downdip. During the final few years of the simulation cycle, the average sliding velocity is approximately inversely proportional to the time to occurrence for a large interplate earthquake.