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

在不同的俯冲带的缓慢滑动提供了一个新的机会，研究大地震之间的巨型逆冲断层的状态。俯冲带中的孔隙流体压力升高通常在发生缓慢滑动事件的区域被检测到，但尚不清楚这种高孔隙压力实际上如何与缓慢滑动相关联。该项目通过岩石变形的实验室实验探索流体与缓慢滑动机制之间的联系。该项目将使用一种新的成像技术，动态显微层析成像，这有助于成像岩石样品的内部，因为它是压到故障点。这些实验可以在不同的孔隙压力水平和不同的和可变的速度下进行，以探索可以导致断层从快速滑动到稳定的缓慢滑动的条件范围。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，并减缓存在断层的岩石中的摩擦滑动。不排水条件下的膨胀硬化被认为是负责这些观察到的稳定效果。初步的实验数据表明，高孔隙流体压力也可以阻碍故障的增长名义排水条件下。该项目是一套系统的断裂和摩擦实验，以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）使用动态显微层析成像表征实时微观结构演变。这将导致渗透率，孔隙度和孔隙形状的时空分布的定量评估，从而更好地限制排水条件在脆性破坏; 2）阐明的作用，从粘滑事件的过渡缓慢滑动事件沿着预先存在的故障。研究人员将使用不同的断层泥材料来产生不同的排水条件，并研究高孔隙流体压力和缓慢滑动行为之间的机械联系; 3）识别断层几何形状的诊断特征和与缓慢断层相关的断层外损害。这项研究的结果将导致更好地了解不同的不稳定性和机械过程负责他们。这个奖项反映了NSF的法定使命，并已被认为是值得支持的评估使用基金会的知识价值和更广泛的影响审查标准。

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.