Insights into the seismic hazard of Western Australia

Western Australia (WA) is considered to be a region with a low seismic hazard. However, WA comprises two of the most seismically active regions in the Australian continent which are the northwest of WA and the South West Seismic Zone. These active zones demonstrate that significant earthquake activity can occur in the state and indicate that any major infrastructure projects should include a site specific seismic hazard assessment.

This paper describes recent studies of current and paleoearthquakes which provide insights into the characteristics of the earthquake activity and which should be taken into account when a site specific (deterministic or probabilistic) seismic hazard assessment is undertaken. Some of the earthquake characteristics identified in recent studies and discussed in this paper include:

1. Location of potential earthquake sources away from the current areas of seismicity.
2. Potential for earthquake magnitudes in WA reaching moment magnitudes (MW) up to 7.2 (based on results from paleoseismological studies).
3. Episodic fault behaviour in which periods of earthquake activity on a fault can be separated by long periods of quiescence.
4. Possible migratory and transient character of the seismic activity in the region.

This paper suggests than when considered as part of a site specific seismic hazard assessment, the above characteristics can result in an estimated earthquake hazard which may vary from the seismic hazard detailed in the current earthquake hazard map of Western Australia.