Pattern and origin of the present-day tectonic stress in the Australian sedimentary basins

Abstract

The present-day stress field of Australia has been the subject of great interest in the three past decades because it shows a variable pattern for the orientation of maximum horizontal stress (S Hmax) that is not parallel to absolute plate motion. The last prior release of the Australian Stress Map (ASM) project, published in 2003, contained 549 data records in 16 stress provinces and highlighted the role of plate boundary forces on the regional stress pattern of continental Australia. However, smaller scale rotations of the S Hmax orientation in Australian sedimentary basins were not investigated in great detail in previous studies. Herein, we present the latest release of the ASM with 2140 data records in 30 stress provinces, with a particular emphasis on newly compiled data in eastern Australian basins. The new release of the ASM has stress data from 20 Australian sedimentary basins, which further confirms the regional variability of S Hmax orientations in the Australian continent, and reveals four major trends for the orientation of S Hmax including NE-SW in northern, northwestern and northeastern Australia, E-W in southern half of Western Australia and South Australia, ENE-WSW in most parts of eastern Australia and NW-SE in southeastern Australia. In addition, the 2016 ASM reveals significant rotation of stress within various sedimentary basins due to different geological structures, including basement structures, faults, fractures and lithological contrasts. Understanding and predicting local stress perturbations has major implications for determining the most productive fractures in petroleum and geothermal systems, and for modelling the propagation direction and vertical height growth of induced hydraulic fractures in unconventional reservoirs.