Intra-plate seismicity of the Lake Eyre Basin and Gawler Craton, Australia

Abstract

<p>The Australian continent, being void of plate boundaries, is often perceived as seismically quiescent. However, around 100 magnitude three or larger earthquakes are typically recorded in Australia each year, with a magnitude 6+ occurring every 8-10 years. Such intra-plate activity can pose a significant risk as they are often non-periodic, poorly understood, and sporadically recorded by sparse seismic networks across vast continents. Within Australia the distribution of intra-plate seismicity is non-uniform, but instead tends to concentrate along certain weak zones of increased activity. One such region is the eastern margin of the Gawler Craton in South Australia, one of the oldest building blocks of the continent. Recently several new temporary seismic arrays have been deployed in the region, transforming data coverage across South Australia. So far over 70 new local events have been recorded that would otherwise have gone undetected by the national network. After relocation the pattern of earthquakes becomes more spatially defined and appears to be closely tied to the edge of the Gawler Craton. Supporting evidence suggests that these events may be associated with a trans-crustal scale fault system that adds new constraints on the poorly defined craton boundary.</p>