Legacy product - no abstract available

Legacy product - no abstract available

The contemporary crustal stress regime in south-eastern Australia can be traced back to the terminal Miocene. Increased coupling of the Australian and Pacific Plate boundary at this time resulted in regional-scale tilting, local uplift and erosion, and in the formation of unconformities in southern Australian basins. In the onshore Gippsland Basin the unconformity surface is overlain by an extensive sheet of fluvial sediment known as the Haunted Hill Formation (HHF). Open folds and flexures developed within the HHF over blind reverse and reverse oblique faults provide a record of deformation spanning much of the neotectonic period. The predominance of flexures and folds rather than discrete faulting at the surface complicates the assessment of slip rates over the last few seismic cycles. However, ages from an undeformed fill terrace bordering the Morwell River and crossing the Morwell Monocline suggest that it has been a minimum of 70 ka since the last deformation event on at least this structure. Stream profiles crossing the Snake Ridge, Yallourn and Rosedale Monoclines similarly reveal no evidence for recent tectonic displacement. Cosmogenic radionuclide (10Be and 26Al) burial ages of siliceous sediments sampled from tectonically uplifted HHF on the Yallourn, Morwell and Snake Ridge Monoclines provide constraint on the long-term evolution of these structures. Combined with stratigraphic and tectonic records from the offshore Gippsland Basin, these data provide a basis for informed seismic hazard assessment.

Occurring in the southwest of Western Australia, the 1968 Meckering earthquake (MS 6.8) resulted in the formation of an extensive surface rupture complex comprising faults with a range of orientations and demonstrating reverse and dextral lateral offsets. The rupture extended for approximately 37 km and scarps were as high as 2.5 m high near to the centre of the complex. Modeling of the seismological characteristics of the source show reverse failure occurred on a north-south striking, east-dipping, surface, but how this is related to the local Precambrian bedrock geology is not clear.Interpretation of new aeromagnetic data, together with subsequent ground-truthing, has allowed concealed bedrock lithology and structure to be mapped in previously unachievable detail. These data show that the surface faulting correlates closely with linear magnetic anomalies, interpreted as dykes/faults and lithological contacts. The apparent arcuate form of the fault complex is explained in terms of the reactivation of northeasterly (dykes and faults) and northwesterly (stratigraphic) trending features in a stress regime with an east-west oriented maximum principal stress. Space problems created where these two trends converge led to the creation/reactivation of a linking north-south trending thrust fault which accommodated the greatest displacements recorded for the 1968 event. This interpretation is consistent with previous research on the source parameters of Meckering event, which invoked one or more easterly dipping failure surfaces and reverse slip.

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available