Earthquake fracture damage and feedbacks in the seismic cycle: a multidisciplinary study

地震是地球内部动力学的一种极具破坏性且不可预测的表现。它们对应于沿沿着地质断层的快速运动，当地震波沿沿着断层链传播时产生地震波。破裂沿着断层的传播引起承载断层的岩石的剧烈应力和变形，随着地质时间尺度上沿着沿着发生多个地震，这些岩石变得越来越受损（即退化）。反过来，断层外岩石的这种损伤对动态破裂过程产生影响：损伤产生和地震破裂是耦合现象。因此，更好地了解动态破坏过程可以真正提高我们对地震物理学的理解，从而有助于更好地预测强震和地震灾害。本提案的目标是研究动态破裂如何在围岩中引起损伤，这种损伤的具体特征，它如何影响岩石性质，最后建立了考虑破裂传播与断层外破坏耦合的地震破裂模型。所提出的方法是多学科的，包括：（1）在南加州圣哈辛托断层周围的天然破坏样品的现场表征：（2）在非常高的变形速率下的实验室岩石变形实验;和（3）数值模拟方法的发展，对实验数据进行测试，到目前为止，动态损伤研究中最具挑战性的方面是在变形速率下进行岩石变形实验，与地震破裂有关的压力条件。为了实现这一目标，我们的建议包括设计和建造一种新型的变形装置，这将允许高速压缩和减压试验进行岩石样品。该仪器在欧洲是独一无二的，将涵盖前所未有的变形条件范围。

Earthquakes are a very destructive and yet unpredictable manifestations of the Earth internal dynamics. They correspond to a rapid motion along geological faults, generating seismic waves as they propagate along the fault strands. The propagation of ruptures along faults induces dramatic stresses and deformation of the rocks hosting the fault, which become increasingly damaged (i.e, degraded) as multiple earthquakes occur along a fault over geological timescales. In turn, this damage of the off-fault rocks has an impact on the dynamic rupture processes: damage generation and earthquake rupture are coupled phenomena. A better knowledge of the dynamic damage processes can thus truly improve our understanding of the physics of earthquakes, and hence help to better predict strong motion and earthquake hazard.It is the goal of this proposal to investigate how dynamic ruptures can induce damage in the surrounding rocks, the specific characteristics of this damage, how it affects the rocks properties, and finally to build an earthquake rupture model which includes the couplings between rupture propagation and off-fault damage. The proposed approach is multidisciplinary, and includes: (1) field characterisation of naturally damaged samples around the San Jacinto fault in South California; (2) laboratory rock deformation experiments at very high deformation rates; and (3) the development of a numerical modeling approach, tested against experimental data, which will allow simulations of fully coupled earthquake rupture processes to be performed.By far the most challenging aspect of the study of dynamic damage is to perform rock deformation experiments at deformation rates and pressure conditions relevant to earthquake ruptures. To achieve this, our proposal includes the design and construction of a novel deformation apparatus which will allow high speed compression and decompression tests to be performed on rock samples. This apparatus will be unique in Europe and will cover an unprecedented range of deformation conditions.