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大震改变地壳的应力,从而触发地震及其余震。一系列随时间变化的过程,包括余滑、孔隙流体的流动、下地壳和上地幔粘性的张驰、断层附近应力和孔隙压力调整以及地震的触发进程。然而,尽管进行过多次尝试,但通过直接场地的观测,很难将这些过程区分开来。这里我们采用一种星载雷达干涉图和冰岛南部地震带两个6.5级地震地热井水位变化过程结合的测量法。干涉图记录到的形变既不能用余滑也不能用粘-弹性张驰来解释,但它与地震发生后最初两个月孔隙弹性物质的回跳一致,这可以用地震引起水位变化的快速恢复(1—2个月)来证实,相反余震序列的持续时间达到3.5年,这表明余震的持续时间并不是由孔隙流体的流动控制的,但是,因为表面应变是由地壳浅部孔隙压力的变化控制的,因此,我们不能排除在余震发生深度存在较长时间的孔隙压力瞬态变化。余震的持续时间与随速度和状态变化的摩擦定律控制的地震活动变化速率模型是一致的。
Large earthquakes change the crustal stress, triggering earthquakes and other aftershocks. A series of time-dependent processes, including slip, pore fluid flow, viscoelastic relaxation of the lower crust and upper mantle, stress and pore pressure adjustments near faults, and triggering of earthquakes. However, despite numerous attempts, it is difficult to distinguish these processes by direct site observations. Here we use a combination of the satellite-borne radar interferogram and the geothermal well water level change between two 6.5-magnitude earthquakes in the southern Icelandic seismic zone. The distortions recorded in the interferograms can neither be explained by slip nor visco-elastic relaxation, but they coincide with the rebound of pore elastic in the first two months after the earthquake, which can cause rapid recovery of water level changes with the earthquake ( 1-2 months) to confirm that the duration of the aftershock sequence was 3.5 years, indicating that the aftershock duration was not controlled by the pore fluid flow but because the surface strain was controlled by the shallow pore pressure in the crust Therefore, we can not rule out the transient change of pore pressure which exists for a long time after the aftershock occurs. The duration of aftershocks is consistent with the rate of change of seismic activity controlled by the friction law of velocity and state changes.