Nucleation of Characteristic Earthquakes in Simulated Cycles Involving Deep Huge Slow Slip Events
Nucleation of Characteristic Earthquakes in Simulated Cycles Involving Deep Huge Slow Slip Events
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涉及深部巨大慢滑移事件的模拟循环中特征地震的成核
DOI：
10.1029/2018jb016156
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Nakatani Masao
中科院分区：
文献类型：
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作者：
Ohtani Makiko;Kame Nobuki;Nakatani Masao
1944年托南凯地震和1946年南海大逆冲断层地震很可能在更深的脆韧性过渡带发生了巨大的缓慢滑动事件（SSE），在几天内积累了一米或更大的滑动。本研究通过遵循速率和状态相关摩擦的地震周期模拟来研究这种巨大的SSE与特征地震之间的相互作用。为了模拟巨大的SSE，我们采用了一个截止速度（Vcx），在该速度之上，摩擦从速度减弱到速度加强。我们假设在20 km到35 km深度之间的过渡区，随着深度的增加，Vx从10 m/s减小到10− 9 m/s。根据特征滑动距离Lof速率和状态摩擦，模拟结果显示了三种地震成核模式。如果L很小，则过渡带中的SSE直接发展为地震，而不会在脆性带处经历单独的成核（脆性成核）。如果L是中等的，SSE触发脆性成核，发展成地震。如果L很大，则SSE发生但停止，而不触发地震或脆性成核，然后滑动赤字进一步积累，最终在没有SSE的直接帮助下开始脆性成核，并且地震发生时没有大的前兆。此外，孤立的巨大SSE，类似于偶发性SSE，在所有情况下都会发生，每个周期最多发生几次。
The 1944 Tonankai and 1946 Nankai megathrust earthquakes are likely to have been immediately preceded by a huge slow slip event (SSE) in the deeper brittle‐to‐ductile transition zone, which accumulates slip of a meter or more within several days. The present study investigates the interaction between such huge SSEs and the characteristic earthquakes through earthquake cycle simulations obeying the rate‐ and state‐dependent friction. To simulate huge SSEs, we employ a cutoff velocity (Vcx) above which the friction changes from velocity weakening to velocity strengthening. We assume thatVcxdecreases from 10 to 10−9m/s with depth over the transition zone located between 20‐ and 35‐km depths. Depending on the characteristic slip distanceLof rate and state friction, simulation results showed three patterns of earthquake nucleation. IfLis small, an SSE in the transition zone directly grows into an earthquake without experiencing a separate nucleation at the brittle zone (brittle nucleation). IfLis moderate, an SSE triggers brittle nucleation, which develops into an earthquake. IfLis large, an SSE occurs but ceases without triggering an earthquake nor brittle nucleation, then slip deficit accumulates further to finally start brittle nucleation without the direct help of SSE, and an earthquake occurs without a large precursor. In addition, isolated huge SSEs, resembling precursory ones, occur in all cases, at most a few times per cycle.