Evolution of the Mesozoic-Cenozoic stress fields in Tasmania from fault population analysis

This study reconstructs the Mesozoic-Cenozoic tectonic stress evolution of Tasmania through fault population analysis. A total of 991 mesofaults were measured at 44 sites, spanning rocks from the Cambrian to the Quaternary. Using multiple inversion techniques, 32 statistically significant paleostress tensors from 27 sites were retained based on their mechanical compatibility, statistical significance, and Quality Index. The results indicate a transition from early extensional stress regimes, characterized by horizontal σ 3 axes trending NE-SW to ENE-WSW, to subsequent compressional regimes with dominant ESE-WNW to SE-NW σ 1 orientations. The 14 extensional solutions indicate near-radial extension; three axisymmetric solutions were excluded from the directional analysis, whereas the remaining tensors define a mean σ 3 orientation of N076E. Most compressional solutions indicate transpressional conditions and define a mean σ 1 orientation of N130E, suggesting oblique reactivation of inherited high-angle faults. Subordinate orientations near the Tamar Fracture System and the Arthur Lineament may reflect local strain partitioning, structural inheritance, or temporally distinct deformation. Cross-cutting striations at two sites demonstrate that compression postdated extension, although individual compressional solutions cannot be assigned unequivocally to the mid-Cretaceous or Cenozoic episodes. Inversion of 128 earthquake focal mechanisms yields a present-day strike-slip tensor with subhorizontal WNW-ESE σ 1 , nearly vertical σ 2 , subhorizontal NNE-SSW σ 3 , and a reduced stress ratio of 0.42. Spatial subsets record strike-slip, transpressional, and compressional regimes while maintaining a broadly E-W to NW-SE maximum-compression orientation. The directional agreement between palaeostress and present-day results supports recurrence of a comparable regional compression orientation, but not continuous activity of an invariant stress field.