MECHANICAL STABILITY OF THE REDBANK THRUST ZONE, CENTRAL AUSTRALIA - DYNAMIC AND RHEOLOGICAL IMPLICATIONS

Deep seismic reflection profiling and other studies indicate that the Moho has been significantly displaced by intracratonic deformation on the Redbank Thrust Zone in central Australia. A two-dimensional finite -element model of the thick-skinned crustal structure of the Redbank T hrust Zone shows that the gravitational stresses generated by the dist ribution of crustal masses are in agreement with the tectonic and seis mic quiescence of the area. Rock failure is concentrated in the downth rusted, and therefore rheologically weakened, crustal segments. Conver sely, the upthrusted slices of lower crust and upper mantle undergo li ttle deformation and no failure and thus constitute a mechanically str ong whole-crustal core. The presence of north-south oriented intraplat e stresses derived from far-field plate boundary forces does not contr ibute to the inferred mechanical equilibrium of the crust in central A ustralia. The results may have implications for the mechanical stabili ty of intracratonic thick-skinned crustal structures elsewhere, and fo r the long-term strength of continental lithosphere in general. The mo dels, however, do predict the possibility. of intraplate seismicity in response to small changes in tectonic stress, since parts of the crus t are already at or close to the failure limit.