Finite-element modelling of contemporary and palaeo-intraplate stress using ABAQUS™

Knowledge of the contemporaneous and palaeo-orientation of maximum horizontal compressive stress (S"H"m"a"x) in the Earth's crust is important for the exploration and recovery of hydrocarbons and also provides insights into the mechanisms driving plate motion and intra-plate seismicity. 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 properties. We have used the finite-element method as implemented in the software package ABAQUS(TM) along with the optimisation software Nimrod/O to model the orientations and magnitudes of S"H"m"a"x over the Indo-Australian plate for the present and the Miocene. An elastic 2D plane stress model incorporating realistic mechanical properties for the Australian continent was used consisting of 24,400 elements, providing a resolution of 0.2^o in both latitude and longitude. In general, modelled S"H"m"a"x directions correlate well with observed contemporary stress indicator data and reactivation histories over the NW Shelf and Bass Strait regions of the Australian continent, where Tertiary tectonic reactivation through time is best documented. Large perturbations in S"H"m"a"x orientation over the Australian continent are shown to occur in and around regions of heterogeneous material properties.