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一般认为地震序列的发生意味着不同断层段之间的一种相互作用。每次位错产生的同震应力的传递则是这种相互作用最显著的成分。然而,一个地震系列中各个后续事件之间的时间间隔却表明,同震应力尚不足以单独引发其他的地震。我们研究了同震应力场可能诱发孔隙流体流,改变了所在区域的孔隙压力分布情况。鉴于地壳在很多地区都是一种流体饱和介质,故将地壳视为一种孔隙弹性固体。由于孔隙物质所表现的应力场依赖于时间,所以我们将验证这种性质能否解释余震的触发。我们考察了一些现有的半无限平面断层的解析方法。对可渗透的和不可渗透的位错面均作了考虑。我们将孔隙弹性介质的解法与孔隙介质的解法作了对比,计算了变形与流体扩散之间的耦合效应。结果发现主震产生的库仑应力变化在某些区域初始时可能表现为负值,但尔后随着孔隙流体的重新分布而变为正值。这种变化意义重大。如果地壳确如我们所假定的表现为一种各向同性、充满流体的孔隙弹性介质的话,那么,通过孔隙流体扩散的库仑应力触发作用则很可能是余震产生的重要机制,余震发生的范围分别为长约2.5个断层长度,宽约0.5个断层长度。这个范围小于以前模型的预测值,以前的这些模型都忽略了弹性变形和孔隙流体扩散之间的力学相互作用。对于典型的孔隙结构,流体流引起的应力变化在主震发生后约一年内会有很大程度的衰减。
It is generally accepted that the occurrence of an earthquake sequence implies an interaction between different fault segments. The transmission of coseismic stress generated by each dislocation is the most significant component of this interaction. However, the time interval between subsequent events in a series of seismic series shows that coseismic stress is not sufficient to cause other earthquakes by itself. We study the coseismic stress field may induce pore fluid flow, changing the pore pressure distribution in the region. Since the crust is a fluid saturated medium in many areas, the crust is considered a porous elastic solid. Since the stress field exhibited by the pore material depends on time, we will verify that this property can explain the triggering of aftershocks. We examine some existing methods of semi-infinite plane fault resolution. Both permeable and impermeable dislocation planes are considered. We compare the solution of porous elastic media with the solution of porous media, and calculate the coupling effect between deformation and fluid diffusion. The results show that the Coulomb stress changes produced by the mainshock may show negative values in some regions initially, but then become positive with the redistribution of pore fluid. This change is of great significance. If the crust does behave as an isotropic, fluid-filled pore-elastic medium as we have assumed, then the Coulomb stress triggering through pore fluid diffusion is likely to be an important mechanism for aftershocks and the range of aftershocks occurs separately It has a length of about 2.5 faults and a width of about 0.5 faults. This range is smaller than the predicted values of the previous models, which neglect the mechanical interactions between elastic deformation and pore fluid diffusion. For a typical pore structure, the change in stress caused by the fluid flow can be largely attenuated within about a year of the main shock.