Modelling the contemporary and palaeo stress field of Australia using finite-element modelling with automatic optimisation

Abstract

Knowledge of the contemporary and palaeo-orientation of maximum horizontal compressive stress (SHmax) in the Earth?s crust is important for the exploration and recovery of hydrocarbons, and provides insights into the mechanisms driving plate motion. To date, most approaches for modelling intraplate stress orientations have been based on applying forces to homogeneous elastic plates. However, real tectonic plates consist of oceanic and continental lithosphere, including sedimentary basins, fold belts, and cratons with large differences in elastic parameters. We have used the finite-element method, as implemented in the software package ABAQUSÔ along with the automatic optimisation software Nimrod/O, to model the orientations and magnitudes of SHmax over the Indo-Australian plate for the present and the Miocene. An elastic 2D plane-stress model incorporating realistic mechanical parameters for the Australian continent was used, consisting of 24 400 elements, providing a resolution of 0.2° in both latitude and longitude. In general, modelled SHmax directions correlate well with observed contemporary stress indicator data and reactivation histories over the Northwest Shelf and Bass Strait regions of the Australian continent, where Tertiary tectonic reactivation through time is best documented. Large perturbations in SHmax orientation over the Australian continent are shown to occur in and around regions of heterogeneous material parameters.