The 2018 National Seismic Hazard Assessment for Australia

Since the publication of the Global Seismic Hazard Assessment Project (GSHAP) hazard map in 1999, Australia has stood out as a region of high earthquake hazard among its stable continental region (SCR) peers. But does this assessment reflect our current understanding of earthquake processes and seismic hazard in SCRs? From an Australian perspective, the hazard map underpinning the GSHAP traces its lineage back to the assessment of Gaull and others (1990). This map was modified through a process of expert judgement in response to significant Australian earthquakes (notably the M W 6.2, 6.3 and 6.6 1988 Tennant Creek sequence and the deadly 1989 M W 5.4 Newcastle earthquake). The modified map, developed in 1991, underpins Standards Australia’s structural design actions (AS1170.4–2007[R2018]) to this day.

Geoscience Australia embarked on an update of the seismic hazard model for Australia through the National Seismic Hazard Assessment 2018 (NSHA18) project. The NSHA18 incorporates global best practice and evidence-based science to develop an updated national-scale seismic hazard assessment. Estimates of hazard from the NSHA18 are significantly lower than seismic design values in the current earthquake loading standard at the 1/500-year annual exceedance probability level. The new assessment has challenged long-held notions of seismic hazard for Australia in both the seismological and engineering communities. Furthermore, it underscores the challenges in developing national-scale seismic hazard assessments in slowly-deforming regions like Australia. This talk will focus on enhancements made to modelling seismic hazard and what this might mean for the future or earthquake design in Australia.