Parsons Tom, Malagnini Luca, Akinci Aybige
U.S. Geological Survey, MS-999, 345 Middlefield Road, Menlo Park, CA 94025, USA.
Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, Rome, Italy.
Sci Adv. 2017 Aug 23;3(8):e1700660. doi: 10.1126/sciadv.1700660. eCollection 2017 Aug.
Earthquakes triggered by other remote seismic events are explained as a response to long-traveling seismic waves that temporarily stress the crust. However, delays of hours or days after seismic waves pass through are reported by several studies, which are difficult to reconcile with the transient stresses imparted by seismic waves. We show that these delays are proportional to magnitude and that nucleation times are best fit to a fluid diffusion process if the governing rupture process involves unlocking a magnitude-dependent critical nucleation zone. It is well established that distant earthquakes can strongly affect the pressure and distribution of crustal pore fluids. Earth's crust contains hydraulically isolated, pressurized compartments in which fluids are contained within low-permeability walls. We know that strong shaking induced by seismic waves from large earthquakes can change the permeability of rocks. Thus, the boundary of a pressurized compartment may see its permeability rise. Previously confined, overpressurized pore fluids may then diffuse away, infiltrate faults, decrease their strength, and induce earthquakes. Magnitude-dependent delays and critical nucleation zone conclusions can also be applied to human-induced earthquakes.
由其他远程地震事件引发的地震被解释为对长时间传播的地震波的一种反应，这些地震波会暂时使地壳产生应力。然而，多项研究报告称，地震波通过后会出现数小时或数天的延迟，这很难与地震波施加的瞬态应力相协调。我们表明，这些延迟与震级成正比，并且如果主导的破裂过程涉及解锁一个与震级相关的临界成核区，那么成核时间最适合流体扩散过程。众所周知，远处的地震会强烈影响地壳孔隙流体的压力和分布。地壳包含水力隔离的、加压的区域，其中流体被包含在低渗透率的壁内。我们知道，大地震产生的地震波引起的强烈震动会改变岩石的渗透率。因此，加压区域的边界可能会出现渗透率上升。先前被限制的超压孔隙流体随后可能会扩散开来，渗透到断层中，降低其强度，并引发地震。与震级相关的延迟和成核临界区的结论也可以应用于人为诱发的地震。
