The present-day state of tectonic stress in eastern Australia

Knowledge of the present-day stress is important to understand the dynamics of earthquakes, and to manage the safe and sustainable usage of the underground during storage and exploitation. Eastern Australia hosts several sedimentary basins with large coal-seam gas reserves as well as mines that are critical for Australia's energy and resources. Some of the eastern Australian basins such as the Surat, Gippsland and Otway basins have been proposed as potential CO2 storage sites. In addition, the Sydney Basin in New South Wales is one of Australia's most seismically active areas. This paper examines the state of present-day stress in eastern Australia from variety of sources including wellbore data, focal mechanism solution of earthquakes, hydraulic fracturing and overcoring tests. In particular, this paper presents the state of stresses in the Bowen, Surat, Clarence-Moreton, Sydney, Gunnedah, Gippsland, Galilee, Cooper, Eromanga, Darling and Otway basins. Analysis of stress data in northeastern Australia (i.e., Bowen and Surat basins) shows a regional orientation of NNE-SSW for the maximum horizontal stress (SHmax), which rotates to ENE-WSW in the Clarence-Moreton, Gunnedah, and Sydney basins. The SHmax orientation is EW in the Galilee, Eromanga and Cooper basins, and rotates to NW-SE in the Gippsland and Otway basins in southeastern Australia. In addition to regional variability, significant stress changes (both orientation and magnitudes) at local scales have been observed due to presence of geological structures, which highlight the importance of geology for geomechanical assessment of the basins.