Earthquake risk in South Australia using averaged seismic moment

Abstract

Appreciable variations in seismic activity have been observed along the main earthquake trends in South Australia. In determining the long‐term seismic risk, allowance has to be made for areas of temporary quiescence, which could be the sites of significant earthquakes in the future. Hence, risk maps are often smoothed by grouping seismicity into regions with a uniform activity, the boundaries of which tend to be fairly subjective. In an alternative form of regionalization, activity in localized regions (effectively point sources) is expressed in terms of seismic moment, which is related to strain release or fault displacement, with minimum assumptions made about the extent of the active areas. The frequency of occurrence of ground motions at a given distance from a source region is obtained from the recurrence and attenuation relations, and the contributions from all active source elements are summed to give the risk at a particular site. In this approach, all the available seismicity data can be used, t...