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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.

向地壳中注入流体会引起地震。在地热刺激、能源储存和回收以及碳固存方面存在这种风险。一个戏剧性的例子是美国中部地震的迅速增加。了解诱发地震活动对于评估和减轻风险至关重要。然而，由于现场地质复杂，材料特性不确定，因此具有挑战性。实验室实验提供了关于注入流体如何引发地震的重要信息。在这里，研究人员使用理论分析和数值模拟来研究流体加压对岩石摩擦滑动的影响。将模拟结果与实验观测结果进行比较，研究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达到的条件下测试参数。在这里，它们用于将实验结果外推到现场观察的时间和尺度。该项目还支持在西北大学（IL）的研究生和本科生的培训。其结果改善了与诱发地震活动相关的灾害评估。更具体地说，该项目研究了孔隙压力变化率对速率和状态摩擦滑动稳定性的影响。这项工作的动机是最近的实验，以不同的速度施加压力。结果表明，加速滑动事件的滑动速度和剪应力降与孔隙压力速率相关，而与孔隙压力的大小无关。对一个简单的弹簧-滑块模型的数值模拟表明，压力率可以控制快速滑动事件的频率，该模型假设滑动由速率和状态摩擦决定。模型的改进表明在实验室中观察到的滑动事件的特征如何取决于摩擦参数，加载速率，孔隙压力增加的速率和幅度，以及扩散率。这项工作提供了一个基本的基础，了解孔隙压力率的影响，伴随着在实验室测试和现场sites.This奖项的注入流体反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。