Geomechanical and seismological investigations of earthquake processes

自然和人为的地震活动对社会构成了风险。对地震物理学有扎实的了解是至关重要的，这样才能预测并尽可能减少地震风险。这项研究计划将地质力学和地震学研究结合到地震物理学中。结合质点方法将用于模拟地震破裂的力学方面，以调查应力模式、事故率、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遥测测量来反转地震周期中应力状态的变化。我们还将使用再次结合粒子方法研究静态触发与动态触发在维持和创建新破裂方面的相对重要性。动态和静态应力扰动都会引发故障，特别是在系统接近临界应力的情况下。因此，了解它们的相对重要性对于预测失败的终结至关重要。 此外，我们将跟踪完整的能量收支，从而准确地划分为破裂过程中的动能、势能、断裂能和摩擦损失，以了解破裂的基本方面，并验证常用的经验关系，以估计应力降和破裂传播速度。 地震调查将补充和验证从地质力学模型中获得的见解。由于正在进行的研究，申请者可以获得在水力压裂治疗过程中发生人为地震活动的工业数据集。这些数据集将得到公开的自然和诱发地震活动数据的补充。此外，访问测量低频变形的光纤数据将允许检查微地震事件发出的快速破裂和例如由于体积变化而在流体注入期间产生的缓慢应变变形。 该研究项目将为11名HQP提供培训：3名学士、3名硕士、2名博士生和3名博士后。HQP将在地质力学建模、观测和理论地震学方面获得有针对性的培训。 这项研究计划的成果预计将造福于社会，而不仅仅是所获得的科学见解和知识。更好地理解破裂结束的原因可能会对自然和诱发地震活动的最大程度提供相关的见解，这反过来又会对地震危险性评估产生直接影响。它还可能导致加强缓解战略，以减少在非常规石油和天然气作业和/或工程地热系统中诱发地震活动的可能性。

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.