Pore Creation due to Fault Slip in a Fluid-permeated Fault Zone and its Effect on Seismicity: Generation Mechanism of Earthquake Swarm
Pore Creation due to Fault Slip in a Fluid-permeated Fault Zone and its Effect on Seismicity: Generation Mechanism of Earthquake Swarm
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流体渗透断裂带断层滑移产生的孔隙及其对地震活动的影响：震群发生机制
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
T. Yamashita
中科院分区：
文献类型：
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作者：
T. Yamashita
摘要破裂活动的时空变化是模拟假设流体迁移在一个狭窄的多孔断层带形成的沿着垂直走滑断层在半无限弹性介质。孔隙被认为是由断层滑动在断层带中产生的。有效应力原理与库仑破坏准则相结合，引入了断层滑动与孔隙流体之间的力学耦合。流体被假定为流出的局部高压流体隔间中的故障与地震破裂的开始。地震序列的持续时间被假定为比断层上特征事件的复发周期短得多。破裂过程被证明是显着依赖于孔隙创建的速率。如果地震率足够大，前震-主震序列就永远不会被观测到。当渗透率的空间分布中引入不均匀性时，破裂活动的时空变化具有高度的复杂性。例如，中等规模事件的频率-震级统计服从古腾堡-里希特关系。当孔隙生成速率较大时，可以模拟具有震群特征的破裂序列。这样的层序一般是逐渐开始和结束的，在层序中没有单一的事件占主导地位。此外，B值显示为异常大。这与地震学对震群的观测是一致的。
Abstract—Spatio-temporal variation of rupture activity is modeled assuming fluid migration in a narrow porous fault zone formed along a vertical strike-slip fault in a semi-infinite elastic medium. Pores are assumed to be created in the fault zone by fault slip. The effective stress principle coupled to the Coulomb failure criterion introduces mechanical coupling between fault slip and pore fluid. The fluid is assumed to flow out of a localized high-pressure fluid compartment in the fault with the onset of earthquake rupture. The duration of the earthquake sequence is assumed to be considerably shorter than the recurrence period of characteristic events on the fault. The rupture process is shown to be significantly dependent on the rate of pore creation. If the rate is large enough, a foreshock–mainshock sequence is never observed. When an inhomogeneity is introduced in the spatial distribution of permeability, high complexity is observed in the spatio-temporal variation of rupture activity. For example, frequency-magnitude statistics of intermediate-size events are shown to obey the Gutenberg–Richter relation. Rupture sequences with features of earthquake swarms can be simulated when the rate of pore creation is relatively large. Such sequences generally start and end gradually with no single event dominating in the sequence. In addition, the b values are shown to be unusually large. These are consistent with seismological observations on earthquake swarms.