What controls Coulomb stress changes on thrust and normal faults? Insights from three-dimensional finite-element models including pore fluid pressure changes and postseismic viscoelastic relaxation

什么控制着逆冲断层和正断层上的库仑应力变化？

• 批准号: 437915117
• 负责人: Professorin Dr. Andrea Hampel
• 金额: --
• 依托单位: Institut für Geologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/437915117?language=en
• 关键词: What; controls; Coulomb; stress; changes

Earthquakes on intra-continental faults pose a substantial seismic hazard to populated areas but their potential to cause major earthquakes has received less attention than the earthquake hazard at plate boundaries. Recent examples of devastating intra-continental earthquakes include the 2008 Wenchuan (China) earthquake and the 2009 L'Aquila and 2016 Norcia-Amatrice (Italy) events. In addition to the immediate damage, a large earthquake on a source fault causes stress changes on adjacent faults (= receiver faults), which may ultimately trigger or delay other earthquakes. The alteration of a receiver fault's stress state is typically expressed in terms of Coulomb stress changes, which are caused by the coseismic displacement and transient postseismic processes including poroelastic effects and viscoelastic relaxation. So far, many studies of Coulomb stress changes have focussed on individual earthquakes and faults in nature, for which the contributions of transient and non-transient processes often remain highly controversial. The main reason for this ambiguity is that the direct measurement of Coulomb stress changes is currently impossible and that Coulomb stress change analyses are therefore based solely on model calculations, which must use simplifying assumptions concerning fault geometry or the implementation of transient processes. For example, the widely used software Coulomb does not consider poroelastic or viscoelastic effects at all. In addition, there is a lack of conceptual models that provide information on theoretically expected stress change patterns and a base for comparison with stress changes induced by natural earthquakes.The goal of the proposed project is to advance our understanding how transient and non-transient mechanisms control co- and postseismic Coulomb stress changes on intra-continental thrust and normal faults. As a method, we will apply 3D finite-element modelling with the software ABAQUS. The model faults will be implemented as frictional contact interfaces, which accumulate slip according to the temporarily evolving stress and strain fields in the model. In different experiment, we will vary the dip and dip direction of the receiver faults as well as their positions with respect to the source fault. All models will include gravity, isostasy and a regional stress field owing to extension or shortening of the model. As causes of Coulomb stress changes, the earthquake magnitude, poroelastic effects, postseismic viscoelastic relaxation and interseismic stress accumulation will be considered. By implementing this range of processes, we will provide the first systematic evaluation of their relative importance for co- and postseismic Coulomb stress changes. Furthermore, we will provide a detailed analysis of the spatial and temporal scales of the different processes, which will enable a better differentiation between poroelastic effects and postseismic viscoelastic relaxation in natural Coulomb stress change patterns.

大陆内部断层上的地震对人口密集地区构成了巨大的地震危险，但它们引起大地震的可能性受到的关注不如板块边界上的地震危险。最近的破坏性大陆内地震的例子包括2008年汶川（中国）地震和2009年拉奎拉和2016年诺西亚-阿马特里切（意大利）事件。除了直接的破坏外，震源断层上的大地震会引起邻近断层（=接收断层）的应力变化，这可能最终引发或延迟其他地震。接收断层应力状态的变化通常用库仑应力变化来表示，库仑应力变化是由同震位移和震后瞬态过程（包括孔隙弹性效应和粘弹性松弛）引起的。迄今为止，许多库仑应力变化的研究都集中在自然界中的单个地震和断层上，瞬态和非瞬态过程的贡献往往存在很大争议。这种模糊性的主要原因是库仑应力变化的直接测量目前是不可能的，因此库仑应力变化分析仅基于模型计算，必须使用简化的假设有关断层几何形状或瞬态过程的实施。例如，广泛使用的软件Coulomb根本不考虑多孔弹性或粘弹性效应。此外，有一个缺乏的概念模型，提供信息的理论上预期的应力变化模式和一个基础，与应力变化引起的天然earthquakes.The拟议项目的目标是促进我们的理解瞬态和非瞬态机制如何控制同和震后库仑应力变化的大陆内逆冲断层和正断层。作为一种方法，我们将应用三维有限元建模软件ABAQUS。模型断层将被实现为摩擦接触界面，其根据模型中暂时演变的应力和应变场累积滑动。在不同的实验中，我们将改变接收断层的倾角和倾角方向以及它们相对于源断层的位置。由于模型的延长或缩短，所有模型都将包括重力、等值线和区域应力场。作为库仑应力变化的原因，将考虑地震震级、孔隙弹性效应、震后粘弹性松弛和震间应力积累。通过实施这一系列的过程中，我们将提供第一个系统的评价，他们的相对重要性的共同和震后库仑应力变化。此外，我们将提供一个详细的空间和时间尺度的不同的过程，这将使孔隙弹性效应和震后粘弹性松弛自然库仑应力变化模式之间的更好的区分。