Slip weakening as a mechanism for slow earthquakes
Slip weakening as a mechanism for slow earthquakes
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DOI：
10.1038/ngeo1818
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发表时间：
2013-06-01
影响因子：
18.3
通讯作者：
Kopf, Achim J.
中科院分区：
文献类型：
--
作者：
Ikari, Matt J.;Marone, Chris;Kopf, Achim J.
缓慢滑动形成了稳定蠕变和破坏性地震之间的断层行为谱的一部分（1，2）。缓慢滑动发生在大地震破裂带的边界附近（3，4），有时可能触发快速地震（2）。它被认为发生在断层中，断层由在快速滑动速率下加强的岩石组成，防止了正常地震的破裂，或者发生在孔隙流体压力升高的断层上（5-7）。然而，控制慢破裂的过程以及慢地震和正常地震之间的关系仍然是个谜。在这里，我们使用实验室实验来模拟从日本南海俯冲带的浅部采集的天然岩石样品中的断层，在那里观察到了非常低频率的地震-一种缓慢滑动的形式（8-10）。我们发现，断层岩石表现出下降的强度超过毫米级的滑动距离，而不是削弱由于增加速度。然而，在我们的实验室模拟的滑移成核补丁的大小是类似于预期的非常低频地震在南开观察。因此，我们认为，这种类型的断层弱化行为可能会产生慢地震。由于我们的数据的基础上的慢地震的预期行为之间的相似性，正常的地震成核期间，我们建议，某些类型的慢滑可能代表过早逮捕地震。
Slow slip forms part of the spectrum of fault behaviour between stable creep and destructive earthquakes(1,2). Slow slip occurs near the boundaries of large earthquake rupture zones(3,4) and may sometimes trigger fast earthquakes(2). It is thought to occur in faults comprised of rocks that strengthen under fast slip rates, preventing rupture as a normal earthquake, or on faults that have elevated pore-fluid pressures(5-7). However, the processes that control slow rupture and the relationship between slow and normal earthquakes are enigmatic. Here we use laboratory experiments to simulate faulting in natural rock samples taken from shallow parts of the Nankai subduction zone, Japan, where very low-frequency earthquakes-a form of slow slip-have been observed(8-10). We find that the fault rocks exhibit decreasing strength over millimetre-scale slip distances rather than weakening due to increasing velocity. However, the sizes of the slip nucleation patches in our laboratory simulations are similar to those expected for the very low-frequency earthquakes observed in Nankai. We therefore suggest that this type of fault-weakening behaviour may generate slow earthquakes. Owing to the similarity between the expected behaviour of slow earthquakes based on our data, and that of normal earthquakes during nucleation, we suggest that some types of slow slip may represent prematurely arrested earthquakes.