Australia's AUS7 Seismotecotnic Model - A Product of 30 Years of Continuous Improvements of Earthquake Hazard Data, Concepts and Techniques

Session: Seismicity and Tectonics of Stable Continental Interiors
Type: Oral
Date: 4/30/2020
Time: 08:45 AM
Room: 240
Description: 

A seismotectonic model for Australia, developed in the 1990’s, has been continually modified and updated as more information and better techniques become available to estimate seismic hazard in this intraplate setting. Since the last iteration was described in 2016, we have incorporated significant changes to the current model, AUS7. Changes include, i) previously we assumed an equivalence between the magnitudes calculated for the original earthquake catalogue (often M_L) and the Moment Magnitude (M_W) values used by various ground motion models. Current practice is still to use the original magnitude values to compute earthquake magnitude recurrence values but these are now transformed, using M_W magnitude conversion factors from the National Seismic Hazard Assessment 2018 (NSHA18), prior to ground motion recurrence values being computed; ii) calculations at a site using the AUS7 model now includes, as independent seismic sources, all active and neotectonic faults within 70 km as well as all large bedrock faults that are aligned with the current crustal stress regime within 40 km. In an attempt to model the episodic nature of fault activity, we assign three varying factors and give appropriate weights to the uplift rate for each fault to reflect periods of activity and quiescence; iii) Maximum magnitude (M MAX ) values assigned to a source zone were previously based on the number of active or neotectonic faults located within that zone, whereby all large earthquakes were assigned to the fault(s). This methodology is still used for zones nearby to the site under consideration, but for distant zones without fault sources (i.e. all zones beyond 70 km) the fault earthquake activity and the zone earthquake activity is modelled together and the zone is assigned a M_MAX of 7.3; iv) source zone boundaries in the AUS7 model have also changed considerably and the earthquake magnitude recurrence values for these zones have been updated based on a more recent earthquake catalogue. These changes have led to a better understanding of earthquake hazard within Australia.

Presenting Author: Elodie Borleis

Authors