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

2000 年至 2018 年 Novy-Kostel 市周围地震发生过程中渗透率动态、断层弱化和应力条件的相互作用

• 批准号: 537665605
• 负责人: Dr. Thomas Heinze
• 金额: --
• 依托单位: Arbeitsgruppe Hydrogeologie
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/537665605?language=en
• 关键词: interplay; permeability; dynamics; fault; weakening

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.

几十年来，由于各种原因，人们一直怀疑高压流体在地震群的地震成因中的触发和驱动作用，特别是在波希米亚西北部：与mofettes和温泉的空间关系，显示出对地震活动的响应，以及孔隙压力扩散模型与地震迁移模式的匹配是两个最突出的例子。此外，有几个动态水力系统的迹象：CO2浓度的变化脱气在地面匹配GPS测量的水平压缩关闭故障;地震波速度的变化表明在压裂过程中孔隙度的变化;低渗透层的重新激活提供了流体迁移的途径。在本项目中，我们将调查（i）不同断层段的动态渗透率与应力、压力和温度的关系;（ii）由于矿物溶解导致的断层强度降低;以及（iii）局部应力场内的断层几何形状是否是该地区特征地震迁移模式的触发器、驱动力或促进条件。为了解决这些研究问题，我们提出了一个三维的，基于物理的，热-水-力学模型的设计，包括多相，多组分的流动上升的超临界二氧化碳和深层地下水。这种模式的功能远远超过现有的方法，并允许系统地测试不同的假设。由于其三维设计，该模型将是第一个再现应力条件和模拟流体流动沿着复杂的断层几何推导出的力矩张量分析。特别是对于2011年、2014年和2018年的震群，3D几何对于再现这些年地震活动的时空演化至关重要。通过对CO2的状态方程进行简化，考虑CO2的相变、溶解和脱气，该模型避免了对单相流体流动的过度简化假设。此外，通过考虑孔隙度/渗透率的演变与孔隙压力，应力状态和温度，该模型将允许模拟多个地震群，并可能提高我们对地震群的周期性和时空演变的理解。该模型的结果可以与ICDP埃格裂谷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一个独特的机会。总的来说，ICDP埃格裂谷观测站提供了对项目成功至关重要的长期观测历史，包括地层学、流动测量和高质量的地震目录。该项目的结果将揭示渗透率动态的影响，并阐明各种有利的作用，触发和必要的因素，在西波希米亚/沃格特兰地区的不同发生的地震活动。