剪切颗粒层中声致滑动：应用于动力地震触发
Acoustically-induced slip in sheared granular layers: application to dynamic earthquake triggering
摘要：
地震物理学中的一个基本谜团是"遥远的震源如何引发地震？"在这里，我们使用离散元方法模拟颗粒层，在粘滑过程中，受到瞬态振动激励，以进一步了解动态地震触发的物理学。利用库仑摩擦定律的颗粒相互作用，我们观察到延迟触发的颗粒断层泥中的滑动。我们发现，在一个临界振动振幅（应变），有一个突然的过渡，从可忽略的时间提前滑移（时钟提前），以充分的时钟提前，{\it即}，瞬态振动和触发滑移是同时发生的。临界应变为$10^{-6}$量级，与实验室和地球上的观测结果相似。这种转变与颗粒层的摩擦减弱有关，这是由于配位数的急剧减少和接触力网络的减弱。与这种摩擦弱化相关联的是层的弹性模量的显著降低。该研究对触发地震和诱发震波迹象的机制具有重要意义，并指出了断层泥对动态瞬态应力响应的基本过程。
英文摘要：
A fundamental mystery in earthquake physics is ``how can an earthquake be triggered by distant seismic sources?'' Here, we use discrete element method simulations of a granular layer, during stick-slip, that is subject to transient vibrational excitation to gain further insight into the physics of dynamic earthquake triggering. Using Coulomb friction law for grains interaction, we observe delayed triggering of slip in the granular gouge. We find that at a critical vibrational amplitude (strain) there is an abrupt transition from negligible time-advanced slip (clock advance) to full clock advance, {\it i.e.}, transient vibration and triggered slip are simultaneous. The critical strain is order of $10^{-6}$, similar to observations in the laboratory and in Earth. The transition is related to frictional weakening of the granular layer due to a dramatic decrease in coordination number and the weakening of the contact force network. Associated with this frictional weakening is a pronounced decrease in the elastic modulus of the layer. The study has important implications for mechanisms of triggered earthquakes and induced seismic events and points out the underlying processes in response of the fault gouge to dynamic transient stresses.
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