Earthquake aftereffects and triggered seismic phenomena
Earthquake aftereffects and triggered seismic phenomena
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DOI：
10.1007/bf02590135
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发表时间：
1983-04
影响因子：
2
通讯作者：
J. Rice;J. Gu
中科院分区：
文献类型：
--
作者：
J. Rice;J. Gu
分析了地壳大地震延迟后效的物理基础。这些影响的范围显然很广，从先前地震震源区附近的典型余震到触发地下水和变形相关的异常，可能包括距离大地震震源几百公里的其他大地震。本文回顾了这些后效的观测报告，并讨论了它们发生的可能机制。值得注意的是，与代表性的M =7至M =8地震有关的远距离同震应力变化似乎太小，不足以引起所报道的那种后效。然而，它表明，在地壳孕震层的远应力的大幅增加，可以发生松弛过程发生，并提出近似的应力估计。这些松弛过程包括，在一个大概短的时间尺度上可能在一年或更短的顺序，深asependently粘性滑动或集中剪切流向下岩石圈延伸的破裂带，并在一个较长的时间尺度上可能几十年，粘滞流在软流层。在松弛状态下，岩石圈应力变化主要由孕震层承载，基底剪应力的减小使应力变化在岩石圈板块中形成通道，从而使应力随距离衰减的速度变慢，因此，大地震附近的断层段经历了突然的同震应力变化，由于上述松弛过程，局部构造加载速率的改变在更远的距离上似乎更重要。在这个意义上，一个大地震可以触发延迟地震或asepersion现象在其他地方.使用一个特定的实验驱动的速率和发展状态的摩擦滑移本构描述，本文结束了一个单自由度断层模型的瞬态滑移响应的初步分析，这种类型的应力扰动。取决于材料性质，特别是取决于断层面是否表现出长期的速度增强或减弱，取决于与其周围环境相互作用的断层刚度的正应力依赖性测量，以及取决于应力扰动的大小和断层面的预扰动状态，响应可能涉及加速到延迟地震不稳定性或瞬时加速然后减速的滑动运动，以一种简单的方式实现应力松弛。在相平面中引入了稳定域的概念，其点位于表面的所有可能的条件，并且报告了该域的边界对刚度和本构性质的依赖性。
The physical basis for delayed aftereffects of large crustal earthquakes is analyzed. These effects apparently range in scale from typical aftershocks near the source region of a prior earthquake to the triggering of groundwater and deformation related anomalies, possibly including other large earthquakes, at locations as much as a few hundred kilometers from the source of a great earthquake. Observational reports of such aftereffects are reviewed and possible mechanisms for their occurrence are discussed.It is noted that distant coseismic stress changes associated with representativeM=7 toM=8 earthquakes seem far too small to induce aftereffects of the type reported. It is shown, however, that a substantial increase of distant stresses in the crustal seismogenic layer can occur as relaxation processes take place, and approximate stress estimates are presented. These relaxation processes include, on a presumably short time scale possibly on the order of a year or less, deep aseismic viscous slip or concentrated shear flow on downward lithospheric extensions of the rupture zone and, on a longer time scale of possibly tens of years, viscous flow in the asthenosphere. The higher stresses occur in the relaxed condition first because lithospheric stress changes are then carried predominantly by the seismogenic layer, and second because the alleviation of base shear stress causes stress alterations to be channeled in the lithospheric plate, consequently causing less rapid stress attenuation with distance.The conclusion is that a fault segment in the vicinity of a large earthquake experiences a sudden coseismic stress change and, as seems more important at greater distances, an alteration in local tectonic loading rate due to the relaxation processes mentioned. In this sense a large earthquake can trigger delayed seismic or aseismic phenomena elsewhere.Using a specific experimentally motivated rate and evolving state constitutive description for frictional slip, the paper closes with an elementary analysis of the transient slippage response of a single-degree-of-freedom fault model to stress perturbations of this type. Depending on material properties, especially on whether the fault surface exhibits long-term velocity strengthening or weakening, on a normal stress-dependent measure of fault stiffness in interaction with its surrounding, and on the size of the stress perturbations and preperturbation state of the fault surface, the response may involve slip motions that accelerate to a delayed seismic instability or that transiently accelerate and then decelerate in rate, accomplishing stress relaxation in an aseismic manner. The concept of a stability domain is introduced in a phase plane whose points locate all possible conditions of the surface, and the dependence of the boundary of this domain on stiffness and constitutive properties is reported.