Finite element analysis of the propagation of Earth’s surface deformation as a consequence of normal dip-slip offshore fault rupture

Abstract

This paper addresses the deformation response of seabed sands subject to underlying normal fault movement. This problem is relevant to the design of overlying offshore structures and subsea oil/gas pipelines connecting offshore platforms to the shoreline. The mechanism of the fault propagation in overlying seabed deposits is examined using 2D finite element modeling. Abaqus© is used as a numerical platform in modeling this complex problem, while accounting for nonlinear soil behavior with strain softening. Different dip angles and vertical fault displacements of up to 10% of the soil layer thickness were considered. The results include the effect of the relative density of the seabed sands and the soil layer thickness on the extent and magnitude of ground surface deformations. The required bedrock displacement/offset for the rupture to reach the surface and the length and location of the distorted zone are also investigated. Based on the parametric analyses and results presented in this paper, observations related to the potential magnitudes and extents of surface deformations for various conditions of seabed densities and thicknesses are provided. These would be of importance in determining likely effects of distortion/loading on pipelines and offshore structures crossing the fault zone.