Feedbacks between faulting and fluid flow throughout the seismic cycle: An experimental approach

在地壳中，流体无处不在，存在于岩石的孔隙和裂缝中。在构造活跃区，例如沿着主要的地壳断层或板块边界，岩石变形、破裂和破裂，这通过压实(例如，由于颗粒粉碎导致开放的孔隙坍塌)或膨胀(新的开放的裂缝的产生和扩展)来改变孔隙空间。这些孔隙空间的变化产生了局部流体压力的变化，也对流体通过岩石和断层的能力产生了很大影响。有趣的是，流体压力和流体流动模式也对岩石的变形产生影响，因此形成了复杂的反馈，决定了断层的总体强度和地壳的长期构造。因此，我们对地壳断层力学的理解关键依赖于我们对地壳中孔隙压力时空分布的了解。目前，我们对岩石中变形、流体压力和流体流动之间反馈过程的定量理解受到了我们现场测量岩石性质的能力的限制，这是大规模模型预测所必需的。限制我们理解的一个关键问题是，岩石变形、流体压力和流动是通过脆性破坏之前、期间和之后发生的巨大但非常局部的孔隙度变化来耦合的。因此，拟议的研究的目标是通过进行创新的实验室实验来消除这一知识鸿沟，这些实验利用一系列新开发的流体压力传感器能够监测变形过程中局部和快速的压力变化。通过在实验室岩石样品周围放置这种传感器的3D阵列，我们将监测(1)准静态和动态破裂过程中膨胀/压实的时空定位，以及(2)流体传输特性中的非均质性和各向异性的发展。最终，我们的实验结果将为断裂带物理性质的时间演化提供关键，这些物理性质目前尚不可用，但对于充分评估孔隙流体压力在地壳变形和断裂过程中的作用至关重要。

In the Earth's crust, fluids are ubiquitous in the pores and cracks present in rocks. In tectonically active areas, for instance along major crustal faults or plate boundaries, rocks deform, crack and fail, which modifies the pore space by either compaction (for instance, collapse of open pores due to grain crushing) or dilation (generation and propagation of new open cracks). These changes in pore space generate local fluid pressure variations and also have a great impact on the ability of fluids to move through rocks and faults. Interestingly, the fluid pressure and fluid flow patterns also have an impact on the deformation of rocks, therefore forming complex feedbacks that determine the overall strength of faults and the long-term tectonics of the Earth's crust. Our understanding of crustal fault mechanics therefore relies crucially on our knowledge of the spatio-temporal distribution of pore pressure in the crust.Our quantitative understanding of the feedback processes between deformation, fluid pressure and fluid flow in rocks is currently limited by our ability to measure in-situ rock properties, which are required for large scale model predictions. One of the key problem limiting our understanding is that rock deformation and fluid pressure and flow are coupled through large but very local porosity changes occurring prior to, during and after brittle failure.The goal of the proposed research is, therefore, to unlock this knowledge gap by conducting innovative laboratory experiments that make use of an array of a newly developed type of fluid pressure transducer capable of monitoring local and rapid changes in pressure throughout deformation. By positioning a 3D array of such transducers around laboratory rock samples, we will monitor (1) spatio-temporal localisation of dila- tancy/compaction during quasi-static and dynamic rupture, and (2) the development of heterogeneity and anisotropy in fluid transport properties. Ultimately, our experimental results will provide the key to the time-evolution of fault zone physical properties that are currently unavailable, but which are essential to fully evaluate the role of pore fluid pressure during deformation and faulting in the crust.