Effect of Pore Pressure Rate on Rate and State Frictional Slip In Experiments

实验中孔隙压力速率对速率和状态摩擦滑移的影响

基本信息

批准号：
2120374
负责人：
John Rudnicki
金额：
$ 22.42万
依托单位：
Northwestern University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2021
资助国家：
美国
起止时间：
2021-09-01 至 2024-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2120374&HistoricalAwards=false
关键词：
Effect Pore Pressure Rate State

项目摘要

Injection of fluid into the Earth’s crust can cause earthquakes. Such risks exist in the context of geothermal stimulation, energy storage and recovery, and carbon sequestration. A dramatic example is the rapid increase of earthquakes in the central US. Understanding induced seismicity is critical to assess and mitigate the risks. Yet, it is challenging because of the complex geology of field sites and uncertainty on material properties. Laboratory experiments provide essential information about how injecting fluids may trigger earthquakes. Here, the researchers use theoretical analysis and numerical simulations to study the effects of fluid pressurization on rock frictional slip. Comparing simulations with experimental observations, they examine how pore pressure changes affect fault sliding. Computer simulations allow testing parameters at conditions unattainable in the laboratory. Here, they are used to extrapolate experimental results to the time and scales of field observations. The project also supports the training of graduate and undergraduate students at Northwestern University (IL). Its outcomes improve the assessment of hazards associated with induced seismicity.More specifically, the project examines the effects of imposed rate of pore pressure change on the stability of rate and state frictional slip. The work is motivated by recent experiments that impose pressure at different rates. These show that the slip velocity and shear stress drop of accelerated slip events correlate with pore pressure rate rather than the magnitude of the pore pressure. Numerical simulations for a simple spring – slider model assuming sliding is governed by rate and state friction - show that the pressure rate can control the frequency of rapid slip events. Refinement of the model indicates how the features of slip events observed in the laboratory depend on frictional parameters, rate of loading, rate and magnitude of pore pressure increase, and diffusivity. This work provides a fundamental basis for understanding the effects of pore pressure rate accompanying injection of fluids in laboratory tests and at field sites.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.

将液体注入地球的地壳中会导致地震。这种风险存在于地热刺激，能源存储和恢复以及碳固相的背景下。一个戏剧性的例子是美国中部地震的迅速增加。了解诱导的地震性对于评估和减轻风险至关重要。然而，由于现场地点的复杂地质和材料特性的不确定性，这是具有挑战性的。实验室实验提供了有关注射流体如何触发地震的基本信息。在这里，研究人员使用理论分析和数值模拟来研究流体压力对岩石过滤滑动的影响。将模拟与实验观察结果进行比较，他们检查了孔隙压力变化如何影响断层滑动。计算机模拟允许在实验室无法实现的条件下测试参数。在这里，它们被用来推断实验结果到场观测的时间和尺度。该项目还支持西北大学（IL）的研究生和本科生的培训。它的结果改善了对诱发地震性相关的危害的评估。更具体地说，该项目检查孔压力变化速率对速率和州摩擦滑移的稳定性的影响。这项工作是由最近以不同速率施加压力的实验激励的。这些表明，加速滑移事件的滑动速度和剪切应力下降与孔隙压力速率而不是孔隙压力的大小相关。简单弹簧的数值模拟 - 假设滑动的滑块模型由速率和状态摩擦约束 - 表明压力速率可以控制快速滑移事件的频率。该模型的细化表明了在实验室中观察到的滑移事件的特征如何取决于摩擦参数，填充速率，孔隙压力增加的速率和幅度以及扩散率。这项工作为理解孔隙压力率的影响提供了基本依据，涉及在实验室测试和现场地点注射烟道。该奖项反映了NSF的法定任务，并通过使用基金会的智力优点和更广泛的影响审查标准来评估，被认为是珍贵的支持。