Effects of changes in temperature and fluid pressure on dynamic earthquake rupture in a thermo-poroelastic medium

温度和流体压力变化对热多孔弹性介质中动态地震破裂的影响

基本信息

批准号：
15540401
负责人：
YAMASHITA Teruo
金额：
$ 1.15万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15540401/
关键词：
pooelastic nedia earthquake fault slip weakening 熱多孔性媒質地下流体流体熱断層帯

项目摘要

We theoretically study thermo-hydraulic effects on dynamic earthquake rupture. First, the system of governing equations is derived assuming a thereto-poroelastic medium, and then numerical calculations are carried out based on these equations. Non-linear feedbacks among changes in temperature, fluid pressure and fault slip are shown to play important roles in the rupture dynamics. For example, the duration of fault slip is found to be longer than expected from the classical Griffith crack model located in an elastic medium because of these feedbacks ; the deviation from the solution for the Griffith crack model is larger when the thickness of heated fault zone is larger. The feedbacks also produce slip-weakening behavior and gradual slip onset. Slip-weakening distance is shown to be larger when the rate of fluid outflow from the heated fault zone is larger. A tendency is also found in our simulations that smaller-size events have smaller stress drops, which is consistent with some seismological observations ; the difference in the stress drop between small-and large-size events is larger when the permeability of the medium is smaller. This occurs because ongoing fault slip tends to raise fluid pressure. Our simulations in this paper suggest that scaling relation between small-and large-size earthquakes are rather complicated because of thermo-hydraulic effects.

我们从理论上研究了动态地震破裂的热水力效应。首先，假设多孔弹性介质导出控制方程组，然后基于这些方程进行数值计算。温度、流体压力和断层滑移变化之间的非线性反馈在破裂动力学中发挥着重要作用。例如，由于这些反馈，发现断层滑动的持续时间比位于弹性介质中的经典格里菲斯裂缝模型预期的要长；当加热断层带厚度越大时，与Griffith裂纹模型解的偏差就越大。这些反馈还会产生滑动减弱行为和逐渐开始滑动。当流体从加热断裂带流出的速率越大时，滑移弱化距离就越大。在我们的模拟中还发现了一个趋势，即较小规模的事件具有较小的应力降，这与一些地震学观察结果一致；当介质的渗透率较小时，小尺寸事件和大尺寸事件之间的应力降差异较大。发生这种情况是因为持续的断层滑动往往会升高流体压力。我们在本文中的模拟表明，由于热水力效应，小地震和大地震之间的尺度关系相当复杂。