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Experimental Investigation of Mechanisms for High Pore Fluid Pressure Associated Slow Faulting

高孔隙流体压力伴慢断层机理的实验研究

基本信息

批准号：
2218314
负责人：
Wen-Lu Zhu
金额：
$ 39.83万
依托单位：
University of Maryland, College Park
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2022
资助国家：
美国
起止时间：
2022-07-01 至 2025-06-30
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2218314&HistoricalAwards=false
关键词：
Experimental Investigation Mechanisms Pore Fluid

项目摘要

Slow slip at various subduction zones provides a new opportunity to study the state of megathrust faults in between great earthquakes. Elevated pore fluid pressure in the subduction zone is often detected in regions where slow slip events occur, but it is not well understood how this high pore pressure is actually linked to the slow slip. This project explores this link between fluids and the mechanisms for slow slip through laboratory experiments on how rocks deform. The project will use a new imaging technique, dynamic microtomography, that helps image the interior of a rock sample as it is pressed to the point of failure. These experiments can be conducted at different levels of pore pressure and at different and variable speeds to explore the range of conditions that can lead a fault to move from fast slip to steady slow slip.Recent experimental studies show that high pore fluid pressure can stabilize both fault propagation in intact rocks and decelerates frictional slip in rocks with an existing fault. Dilatant hardening under undrained conditions is thought to be responsible for these observed stabilization effects. Preliminary experimental data show that high pore fluid pressure can also impede fault growth under nominally drained conditions. This project is a systematic set of fracture and friction experiments to understand the role of elevated pore fluid pressure on stabilizing faulting and frictional slip. The goal is to 1) characterize the real-time microstructure evolution using dynamic microtomography. This will result in a quantitative assessment of the spatio-temporal distributions of permeability, porosity, and pore shape, thus better constraints of the drainage conditions during brittle failure; 2) elucidate the role of dilatant hardening in the transition from stick-slip events to slow slip events along a pre-existing fault. The researchers will use different gouge materials to produce different drainage conditions and investigate the mechanical link between high pore fluid pressure and slow slip behaviors; 3) identify diagnostic characteristics of fault geometry and off-fault damage associated with slow faulting. The findings of this study will lead to a better understanding of different instabilities and the mechanical processes responsible for them.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.

各个俯冲带的慢滑移为研究大地震之间的巨型逆冲断层的状态提供了新的机会。在发生慢滑移事件的区域经常检测到俯冲带中孔隙流体压力升高，但目前尚不清楚这种高孔隙压力实际上如何与慢滑移相关。该项目通过岩石变形的实验室实验探索流体与缓慢滑移机制之间的联系。该项目将使用一种新的成像技术，即动态显微断层扫描，当岩石样本被压到失效点时，该技术有助于对岩石样本的内部进行成像。这些实验可以在不同的孔隙压力水平和不同的可变速度下进行，以探索导致断层从快速滑动移动到稳定慢滑动的条件范围。最近的实验研究表明，高孔隙流体压力可以稳定完整岩石中的断层传播，并减缓现有断层岩石中的摩擦滑动。不排水条件下的膨胀硬化被认为是造成这些观察到的稳定效果的原因。初步实验数据表明，在名义排水条件下，高孔隙流体压力也会阻碍断层生长。该项目是一套系统的断裂和摩擦实验，旨在了解升高的孔隙流体压力对稳定断层和摩擦滑动的作用。目标是 1) 使用动态显微断层扫描来表征实时微观结构演化。这将导致对渗透率、孔隙度和孔隙形状的时空分布进行定量评估，从而更好地约束脆性破坏期间的排水条件； 2）阐明膨胀硬化在沿着预先存在的断层从粘滑事件到慢滑事件的转变中的作用。研究人员将使用不同的凿岩材料来产生不同的排水条件，并研究高孔隙流体压力和慢滑移行为之间的机械联系； 3) 识别与慢断层相关的断层几何形状和断层损伤的诊断特征。这项研究的结果将有助于更好地理解不同的不稳定性以及造成这些不稳定性的机械过程。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。