Numerical investigation of secondary-fault rupture propagation through sandy deposits

The increasing urban development in seismic-prone regions, in conjunction with the continuous construction of large-scale lifelines (i.e., road and railway networks, pipelines, etc.) has increased the risk of potential damages due to permanent displacements at the ground surface that can be caused by an earthquake fault rupture. Several recent earthquakes have revealed this risk. Therefore, the problem of fault rupture propagation of a single fault has been thoroughly investigated with field studies, as well as experimental tests and numerical models. Nevertheless, the presence of parallel or intersecting secondary fault ruptures is usually observed in the field due to stress redistributions and/or rock heterogeneities. The aim of the current study is to examine the rupture patterns and surface displacements caused by the contemporaneous rupture of a main fault and a perpendicular secondary fault. A three-dimensional numerical model has been developed utilizing the finite-element method in order to examine this complex phenomenon in sandy deposits. The soil behavior is represented quite accurately via an elastoplastic Mohr-Coulomb constitutive model with isotropic strain softening, which is initially validated with experimental results obtained by centrifuge tests in case of a single fault. Subsequently, a detailed parametric study has been performed, investigating different fault types and dip angles, as well as sandy layer thickness and material properties, to highlight various important aspects regarding the development and propagation of secondary fault ruptures and the resulting zones of excessive surface displacements.

Automated summary

The study aims to examine the rupture patterns and surface displacements caused by the contemporaneous rupture of a main fault and a perpendicular secondary fault using a three-dimensional numerical model in sandy deposits.