Controls of Pore Fluid Pressure on Fault Slip Weakening and Fracture Energy

孔隙流体压力对断层滑动弱化和断裂能的控制

基本信息

批准号：
1759127
负责人：
Melodie French
金额：
$ 26.48万
依托单位：
William Marsh Rice University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-06-15 至 2024-05-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1759127&HistoricalAwards=false
关键词：
Controls Pore Fluid Pressure Fault

项目摘要

In the past 15 years, measurements from the fields of geodesy and seismology have revealed that large faults along the boundaries of tectonic plates regularly slip at rates slower than earthquakes, but faster than the tectonic plates. These intermediate-rate slip events influence earthquake hazards through their potential to cause an earthquake on an adjacent segment of the fault or to control how big a future earthquake may become. Although the cause of these slip events is still debated, they are consistently observed in regions where the fluids filling pores in the rock are thought to be at very high pressure. Motivated by previous and preliminary laboratory observations that faulting becomes slower and more stable with increasing pore fluid pressure, scientists at Rice University are quantifying the effects of fluid pressure on the physics of faulting. This study is designed to provide inputs into models of regional seismic hazards, including along the San Andreas Fault and in Cascadia, where these slip events have been observed. This research is supporting the development of a laboratory by an early career researcher and the education of one graduate student and several undergraduate students. The researcher and students will incorporate this work into lectures and teaching activities on natural hazards.This research quantifies an experimental observation that is not explained by current models for faulting and, given the abundance of evidence for elevated fluid pressures in fault zones, has direct implications for the cause and characteristics of slow slip. Specifically, previous experimental observations show that the slip weakening distance and fracture energy of faulting increase with fluid pressure. Physical models for fluid pressure stabilization through a process known as dilatant hardening cannot predict the magnitude of this effect or the apparent monotonic decrease in failure rates with increasing fluid pressure. The purpose of this work is to (1) determine the processes that cause stabilization and (2) develop constitutive relations that include the effect of fluid pressure, which can then be incorporated into models of faulting. To this end, researcher and a graduate student are using experimental rock deformation to quantify the slip weakening distance and fracture energy of faulting as a function of pore fluid pressure magnitude and effective stress magnitude.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在过去的15年中，测量和地震学领域的测量表明，沿构造板的边界的大断层经常以比地震速度慢，但比构造板的速度快。这些中级滑移事件通过在断层相邻段引起地震或控制未来地震的大小会影响地震危害。尽管这些滑动事件的原因仍在争论中，但在认为在岩石中充满孔的流体被认为处于非常高的压力的区域中，它们始终被观察到。由先前和初步的实验室观察的动机，即断层随着孔隙压力的增加而变得越来越稳定，赖斯大学的科学家正在量化流体压力对断层物理的影响。这项研究旨在提供对区域地震危害模型的输入，包括沿圣安德烈亚斯断层和卡斯卡迪亚，在那里观察到了这些滑移事件。这项研究正在支持早期职业研究人员的发展实验室，并支持一名研究生和几名本科生的教育。研究人员和学生将将这项工作纳入有关自然危害的讲座和教学活动中。这项研究量化了一个实验观察结果，目前的模型无法解释过故障的模型，并且鉴于大量的断层区域中流体压力升高的证据，对慢滑水的原因和特征具有直接的影响。具体而言，先前的实验观察结果表明，断层的距离弱距离和断裂能量随流体压力增加而增加。通过称为膨胀剂硬化的过程进行流体压力稳定的物理模型无法预测这种效果的大小，或者随着流体压力的增加而明显的单调降低失败率。这项工作的目的是（1）确定引起稳定的过程，以及（2）建立构造关系，其中包括流体压力的效果，然后可以将其纳入故障模型中。为此，研究人员和研究生正在使用实验性岩石变形来量化断层弱距离和断裂能量，这是孔隙流体压力幅度和有效的应力幅度的函数。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子的智力和更广泛的影响来评估的，并被认为是值得的。