Geomechanical and seismological investigations of earthquake processes

自然和人为引起的地震活动对社会构成威胁。为了预测并可能减少地震灾害，对地震物理有一个扎实的了解是至关重要的。这个研究项目将地质力学和地震学研究结合到地震物理学中。结合颗粒方法将用于地震破裂力学方面的建模，以研究应力模式、事件率、最大应力降和震级频率分布之间是否存在系统关系。这种关系将允许仅使用远程可观测的测量来反演地震周期中应力状态的变化。我们还将研究静态触发与动态触发在维持和创造新的破裂中的相对重要性。动态和静态应力扰动都可能引发故障，特别是当系统接近临界应力时。因此，了解它们的相对重要性对于预测故障的终止是至关重要的。

Natural and human-induced seismicity poses a risk to society. It is paramount to have a solid understanding of earthquake physics in order to predict and possibly reduce seismic hazard. This research program combines geomechanical and seismological investigations into earthquake physics. Bonded-particle methods will be used for modeling of the mechanical aspects of earthquake rupture to investigate if systematic relationships exist between stress patterns, event rates, maximum stress drops and the magnitude-frequency distributions. Such relationships will permit to invert for changes in the stress state during earthquake cycles using solely remotely observable measurements. We will also investigate the relative importance of static versus dynamic triggering in both sustaining and creating new rupture using again bonded-particle methods. Both dynamic and static stress perturbations can trigger failure, in particular if the system is close to critically stressed. Understanding their relative importance is thus vital to predict the termination of failure. Furthermore, we will track the full energy budget and thus the exact partitioning into kinetic, potential, fracture energy and frictional losses during rupture to understand the fundamental aspects of rupture but also verify commonly used empirical relationships to estimate stress drops and rupture propagation speeds. Seismological investigations will complement and validate the insights gained from the geomechanical modeling. Because of ongoing research, the applicant has access to industrial datasets where human-induced seismicity occurred during hydraulic fracturing treatments. These datasets will be complemented by publicly available data of both natural and induced seismicity. Furthermore, access to fibre-optic data measuring low-frequency deformation will allow examination of both fast rupture, as emitted by microseismic events, and slow strain deformation, e.g., due to volumetric changes, during fluid injection. This research program will provide training for 11 HQP: 3 BSC, 3 MSc, 2 PhD students and 3 postdocs. HQP will gain pertinent training in geomechanical modeling, observational and theoretical seismology. The outcomes of this research program are expected to benefit society beyond the gained scientific insights and knowledge. An improved understanding of why rupture ends is likely to provide pertinent insights into maximum magnitudes of natural and induced seismicity, which in turn has an immediate impact on seismic hazard assessments. It may also lead to enhanced mitigation strategies to reduce the likelihood of induced seismicity in unconventional oil and gas operations and/or engineered geothermal systems.