Selvadurai P A, Selvadurai A P S
Swiss Seismological Service, Department of Earth and Planetary Sciences, ETH Zurich, Zurich, Switzerland.
Department of Civil Engineering, McGill University, Montréal, QC Canada H3A 0C3.
J Elast. 2025;157(3):44. doi: 10.1007/s10659-025-10135-7. Epub 2025 May 21.
This paper proposes a novel procedure to examine the influences of friction, dilatancy, and normal stresses at fault zones on the estimation of seismic moment. For illustrative purposes, the study focuses on a circular frictional dilatant patch located within a frictionless pre-compressed fault zone undergoing relative shear. When dilatancy occurs, the interface beyond the dilatant region may experience separation due to the normal stresses acting on the fault plane, affecting the deformational response of the pre-stressed asperity. This approach allows for an evaluation of the normal stress on the dilatant region, leading to a re-interpretation of the conventional definition of seismic moment. We compare our model against a comprehensive catalog of earthquakes spanning 16 orders of magnitude, utilizing seismologically inferred source properties as well as data from two separate experimental studies that directly measure the shear-dilatant response of shear fractures in both laboratory and field settings. Our findings indicate that friction-induced dilatancy exerts minimal influence on the estimation of seismic moment. However, we emphasize that the discrepancies between our direct measurements and inferred estimates of seismic moment highlight the need for focused campaigns and in situ and on-fault assessments of earthquake mechanics. . The conventional definition of the has been central to unifying information from plate tectonics, geology, geodesy, and seismology. It looks at how the ground moves along a fault plane and the strength of the surrounding rocks. However, it often overlooks other factors that might affect this movement, such as the stress on the fault and the local topography that can induce additional physical responses. This study explores how these additional factors, particularly a process called dilatancy, can change our understanding of the seismic moment. The authors found that while these factors do play a role, they have a minimal impact on the traditional definition of seismic moment initially proposed by Aki in 1966.
本文提出了一种新颖的方法，用于研究断层带的摩擦力、剪胀性和法向应力对地震矩估算的影响。为便于说明，该研究聚焦于一个位于无摩擦预压缩断层带内的圆形摩擦剪胀斑块，该断层带正在经历相对剪切。当发生剪胀时，由于作用在断层面上的法向应力，剪胀区域之外的界面可能会出现分离，从而影响预应力粗糙面的变形响应。这种方法能够评估剪胀区域上的法向应力，进而对地震矩的传统定义进行重新诠释。我们将模型与跨越16个数量级的综合地震目录进行比较，利用地震学推断的震源特性以及来自两项独立实验研究的数据，这两项研究直接测量了实验室和野外环境中剪切裂缝的剪切 - 剪胀响应。我们的研究结果表明，摩擦引起的剪胀对地震矩的估算影响极小。然而，我们强调，我们直接测量值与地震矩推断估算值之间的差异凸显了开展针对性研究以及对地震力学进行现场和断层评估的必要性。地震矩的传统定义一直是统一板块构造学、地质学、大地测量学和地震学信息的核心。它关注地面如何沿断层面移动以及周围岩石的强度。然而，它常常忽略其他可能影响这种移动的因素，例如断层上的应力以及可引发额外物理响应的局部地形。本研究探讨了这些额外因素，特别是一种称为剪胀的过程，如何改变我们对地震矩的理解。作者发现，虽然这些因素确实起作用，但它们对1966年由赤木最初提出的地震矩传统定义影响极小。
