Tectonic forces controlling the regional intraplate stress field in continental Australia: Results from new finite element modeling

Abstract

The tectonic forces controlling the present-day regional intraplate stress field in continental Australia have been evaluated through a finite element analysis of the intraplate stresses in the Indo-Australian plate (IAP). Constraint for the modeling is provided by an observed regional stress field based on observations in 12 stress provinces. A weighted “basis set” method has been employed to provide an efficient means to evaluate a very large number of tectonic force combinations and to make a quantitative assessment of the fit between the observed and predicted stress fields. Our modeling results indicate that the major features of the regional stress field in continental Australia can be explained in terms of a geologically plausible array of tectonic forces. While the results continue to substantiate that modeling of the Australian intraplate stress field is inherently nonunique, we are nevertheless able to draw a number of fundamental conclusions about the tectonic settings along the principal plate boundary segments including the following: (1) The Himalayan and New Guinea boundaries exert a compressional force on the IAP. (2) Fitting the stress field in the Bowen Basin requires compressional boundary forces along the Solomon and New Hebrides subduction zones directed toward the interior of the IAP. (3) East-west compression in eastern Australia requires a small compressional force along the Tonga-Kermadec subduction zone. (4) Fitting the stress field in southeastern Australia requires compressional forces along the New Zealand, Puysegur Trench, and Macquarie Ridge boundary segments. (5) Significant tensional slab-pull forces exist only along the Java subduction zone.