Slip-rate-dependent friction as a universal mechanism for slow slip events
Slip-rate-dependent friction as a universal mechanism for slow slip events
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DOI：
10.1038/s41561-020-0627-9
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发表时间：
2020-09-07
影响因子：
18.3
通讯作者：
Avouac, Jean-Philippe
中科院分区：
文献类型：
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作者：
Im, Kyungjae;Saffer, Demian;Avouac, Jean-Philippe
世界范围内越来越多的观测记录了断层滑动瞬变，辐射很少或没有地震能量。控制这些慢滑事件（SSE）的机制及其广泛的深度，滑动速率，持续时间，应力降和复发间隔仍然知之甚少。在这里，我们表明，慢滑可以解释为从率弱化摩擦滑动在低滑移率向率中性或率强化行为在较高的滑移率，如实验所观察到的过渡。我们使用数值模拟来说明，这种速率依赖性的过渡定量地解释了实验数据的天然断层岩代表的材料在源区域的SSEs。在标准的常数参数速率-状态摩擦定律下，SSE仅在滑移失稳阈值附近出现。速度相关的摩擦参数的列入大大拓宽了慢滑发生的条件范围，并产生了广泛的事件特征，其中包括应力降，持续时间和复发，在自然界中观察到的。放大的数值模拟，包括参数与实验室测量一致，可以重现大地测量观测重复SSE的构造断层。结果表明，滑动速率相关的摩擦力解释了大范围地质环境中慢滑动事件的普遍存在;数值模拟结果表明，随着滑动速率的增加，摩擦力从速率弱化到速率强化的转变可以解释所观察到的慢滑动事件的多样性。
A growing body of observations worldwide has documented fault slip transients that radiate little or no seismic energy. The mechanisms that govern these slow slip events (SSEs) and their wide range of depths, slip rates, durations, stress drops and recurrence intervals remain poorly known. Here we show that slow slip can be explained by a transition from rate-weakening frictional sliding at low slip rates towards rate-neutral or rate-strengthening behaviour at higher slip rates, as has been observed experimentally. We use numerical simulations to illustrate that this rate-dependent transition quantitatively explains the experimental data for natural fault rocks representative of materials in the source regions of SSEs. With a standard constant-parameter rate-and-state friction law, SSEs arise only near the threshold for slip instability. The inclusion of velocity-dependent friction parameters substantially broadens the range of conditions for slow slip occurrence, and produces a wide range of event characteristics, which include stress drop, duration and recurrence, as observed in nature. Upscaled numerical simulations that incorporate parameters consistent with laboratory measurements can reproduce geodetic observations of repeating SSEs on tectonic faults. We conclude that slip-rate-dependent friction explains the ubiquitous occurrence of SSEs in a broad range of geological environments.A transition from rate-weakening to rate-strengthening frictional behaviour with increasing slip rate could explain the observed diversity of slow slip events on faults, according to numerical simulations.