Northwestern Australia hosts a considerable number of smaller seismic events, but also Australia's largest earthquake on record (Meeberrie, 1941, M7.9). In 2005 we deployed a small network of seismometers to record natural seismicity in the region, to understand the amount, magnitude, nature and distribution of these events, and to interpret these events within a tectonic and neotectonic context. The region is largely underlain by Precambrian material, ranging from Archaean craton to Proterozoic mobile belts, and truncated to the west by the lithospheric-scale Darling Fault. This fault separates the Precambrian crustal elements from the younger Palaeozoic-Mesozoic Carnarvon Basin to the east, has a strike length of over 1400 km. It is thought to have been active since at least the Proterozoic. Estimates of slip on some southerly sections of this fault exceed 12 km. We believe that these various crustal elements (basins, cratons, mobile belts) respond differently to seismicity based on their rheology, thickness and deformation history. We supplemented data from our network with traces from some of the instruments of the national network of Australia. This data set proved adequate for the calculation of fault-plane solutions of some 13 mini- and micro- events in the region. The eventsrecorded occurred along or close to known faults, although field data for movement or reactivation on these faults is sparse. Most of our calculated events occur in close proximity to mechanical boundaries between crustal elements, indicating that the mechanical response of these elements controls the location of seismicity. The transitional tectonic setting of this part of the Australian margin---a passive margin sandwiched between two active margin segments---indicates that the term "intraplate" may be an inappropriate description of these seismic events.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- 7230 Seismicity and tectonics (1207;
- 8107 Continental neotectonics (8002);
- 8164 Stresses: crust and lithosphere