The interplay of permeability dynamics, fault weakening, and stress conditions in the seismogenesis around the city of Novy-Kostel from 2000 to 2018

高压流体在震群，特别是波西米亚西北部的地震发生中的触发和驱动作用，几十年来一直受到各种原因的怀疑：与反映地震活动响应的莫夫岩和温泉的空间关系，以及孔隙压力扩散模型与地震迁移模式的匹配是最突出的两个例子。此外，有几个动态液压系统的迹象：地表二氧化碳浓度的变化与关闭断层的水平挤压的GPS测量相匹配；地震波速度的变化表明压裂过程中孔隙度的变化；低渗透层的重新激活为流体运移提供了路径。在这个项目中，我们将调查(I)不同断层段依赖于应力、压力和温度的动态渗透率；(Ii)由于矿物溶解而导致的断层强度降低；以及(Iii)局部应力场中的断层几何形状，是否是该地区特有的地震迁移模式的触发、驱动力或促进条件。为了解决这些研究问题，我们提出了一种基于物理的三维热流体力学模型的设计，该模型包括了上升的超临界二氧化碳和深层地下水的多相、多组分流动。这种模型的特点远远超过了现有的方法，并允许对不同的假设进行系统的测试。由于其三维设计，该模型将首次再现应力条件，并模拟通过矩张量分析得出的复杂断层几何形状的流体流动。特别是对于2011年、2014年和2018年的地震群，三维几何对于再现这些年地震活动的时空演化是至关重要的。结合二氧化碳的状态方程，考虑二氧化碳的相变、溶解和脱气，该模型避免了对单相流体流动的潜在过度简化的假设。此外，通过考虑孔隙度/渗透率的演化与孔压、应力状态和温度的耦合，该模型将允许模拟多个震群，并潜在地增强我们对地震群的周期性和时空演化的理解。模型结果可以与ICDP Eger Rift天文台的长期测量历史进行比较，这为模型校准和验证提供了独特的机会。总体而言，ICDP Eger Rift天文台提供了对该项目的成功至关重要的长期观测历史，提供了地层学、流量测量和高质量的地震目录。项目结果将揭示渗透率动力学的影响，并阐明各种有利、触发和必要因素在西波希米亚/沃格特兰地区不同地震活动发生中的作用。

The triggering and driving role of high-pressure fluids in the seismogenesis of earthquake swarms, and especially in NW Bohemia, has been suspected since decades for various reasons: the spatial relation with mofettes and thermal springs, which show a response to the seismicity and the match of pore pressure diffusion models with the seismic migration pattern are the two most prominent examples. Further, there are several indications of a dynamic hydraulic system: Variations in CO2 concentrations degassing at the surface match GPS measurements of horizontal compression closing the fault; Changes in seismic wave velocity indicate changes in porosity during fracturing; Reactivation of low permeable layers provide pathways for fluid migration. In this project, we will investigate whether (i) a dynamic permeability of the different fault segments in dependence of stress, pressure and temperature; (ii) a reduced fault strength due to mineral dissolution; and (iii) the fault geometry within the local stress field, are either triggers, driving forces or facilitating conditions for the characteristic seismic migration pattern in the region. To address these research question, we propose the design of a three-dimensional, physics-based, thermo-hydro-mechanical model including multi-phase, multi-component flow of uprising supercritical carbon dioxide and deep groundwater. The features of such a model exceed existing approaches by far and allow a systematic testing of the different hypotheses. With its three-dimensional design, the model will be the first to reproduce the stress conditions and model the fluid flow along the complex fault geometry deduced from the moment tensor analysis. Especially for the swarms of 2011, 2014, and 2018, the 3D geometry is crucial to reproduce the spatio-temporal evolution of the seismic activity in these years. Incorporating the equations of state for CO2, considering phase changes, dissolution, and degassing of CO2 this model avoids potentially over-simplifying assumptions of single-phase fluid flow. Further, by considering a porosity/permeability evolution coupled with pore pressure, stress state, and temperature, this model will allow the simulation of multiple earthquake swarms and potentially enhance our understanding of the periodicity and spatio-temporal evolution of earthquake swarms. The model outcome can be compared with the long history of measurements at the ICDP Eger Rift observatory, which poses a unique opportunity for model calibration and validation. In general, the ICDP Eger Rift observatory provides a long history of observations crucial for the success of the project, with stratigraphy, flow measurements and high-quality seismic catalogs. The projects results will reveal the influence of permeability dynamics and shed light on the role of various favoring, triggering, and requisite factors for the different occurrences of seismic activity in the West-Bohemia/Vogtland region.