Modelling the Bohemian Earthquake Swarms: Application of a poro-thermo-elastic plastic model with weakening, damage and multiphase flow in GPU

我们建议应用一个新开发的模型来数值研究一般的地震群，特别是波西米亚地震群。该模型模拟了孔隙-弹性塑性流变和压力传播的非线性扩散模型，其中非线性是通过渗透率的有效应力依赖性产生的。目前正在实施两相（水和气）流动模型。模型中数值裂纹的形核和扩展响应于；I)在边界处产生远场应力，ii)由内部裂纹扩展引起的应力扰动，以及iii)孔隙弹性应力。最近的发展包括硬化、软化和损伤增长模型，重现了在实验室岩石实验中观察到的整个（加载-破坏-卸载）应力-应变曲线。在本项目中，我们建议：1)加入热流模型并引入热弹性；2)将模型扩展到三维，3)在图形处理单元（GPU）平台上实现模型，4)将模型应用于波西米亚群体。与标准CPU架构相比，GPU平台允许快速和非常高分辨率的模拟。该数值模型模拟了波西米亚地震群的主要物理特性，即CO2注入、地震滑动（伴随渗透率增强）流体流动和对流热流的复杂相互作用和反馈，非常适合研究波西米亚地震群。该模型将用于解决：a)产生群震活动的触发机制，b)表征断层相关的流体输送过程和运移过程中流体/岩石相互作用的影响，以及c)研究系统对压力和温度的依赖。

We propose to apply a newly developed model to numerically investigate earthquake swarms in general and the Bohemian swarms in particular. The model simulates a pore-elastic plastic rheology coupled with a non-linear diffusion model for pressure propagation, where the nonlinearity arises through the effective stress-dependence of the permeability. A two-phase (water and gas) flow model is currently being implemented. Numerical cracks in the model nucleate and grow in response to; i) far-field stresses developed at the boundaries, ii) stress perturbations arising from internal crack growth, and iii) poro-elastic stressing. Recent developments that include hardening, softening, and a damage growth model reproduce the entire (load-failure-unload) stress-strain curve observed in laboratory rock experiments. In this project, we propose to: 1) Include a heat flow model and introduce thermo-elasticity; 2) extend the model to 3-dimensions, 3) implement the model on the Graphics Processing Unit (GPU) platform, and 4) apply the model to the Bohemian swarms. The GPU platform allows fast and very high-resolution simulations in comparison to the standard CPU architecture. The numerical model is ideally suited to study the Bohemian swarms because the dominant physics of the Bohemian earthquake swarms are simulated, namely the complex interactions and feedbacks of CO2 injection, seismic slip (with the concomitant permeability enhancement) fluid flow, and advective heat flow. The model will be used to address: a) triggering mechanisms that generate swarm-earthquake activity, b) characterize fault-related fluid transport processes and effects of the fluid/rock interaction during migration, and c) investigate the system’s dependence on pressure and temperature.