Mmax variation across the Australian stable continental region (SCR) crust derived from the Quaternary faulting record  

Authors / CoAuthors

Clark, D.J. | McPherson, A. | Collins, C.D.N.

Abstract

Probabilistic seismic-hazard analyses (PSHAs) require an estimate of Mmax, the magnitude (M) of the largest earthquake that is thought possible within a specified area. In seismically active areas such as some plate boundaries, large earthquakes occur frequently enough that Mmax might have been observed directly during historic times. In less active regions like Australia, and most of the Central and Eastern United States and adjacent Canada (CEUSAC), large earthquakes are much less frequent and generally Mmax must be estimated indirectly. By virtue of a fortuitous combination of climatic conditions, geology and geomorphology, Australia boasts arguably the richest Quaternary faulting record of all the world's SCR crust. Extensive consultation amongst the geological community, and recent advances in digital elevation model coverage, have allowed the compilation of an inventory of over 200 landscape features consistent with fault scarps relating to Quaternary surface breaking earthquakes across Australia. Variations in the character of these scarps, when considered together with large-scale geological and geophysical variations, justify the division of the continent into six onshore 'neotectonic domains'. Within each domain, mean Mmax has been calculated from the 75th percentile scarp length by averaging the earthquake magnitudes predicted by several published relations. Results range between M7.0-7.5±0.2. While this approach is inherently conservative, extreme values relating to multiple event scarps, which cannot be confidently discriminated without field validation, are removed. Consequently, in several cases our data represent an underestimate of 0.1-0.2 magnitude units relative to calculations based upon rare palaeoseismic data. Nevertheless, our findings indicate the potential for M>7.0 earthquakes across Australia, and by proxy analogous crust in the CEUSAC and elsewhere, and thereby have the potential to significantly reduce uncertainty in PSHAs.

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nonGeographicDataset

eCat Id

71408

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• External PublicationConference Paper

( Theme )

• geohazards

( Theme )

• earthquakes

Australian and New Zealand Standard Research Classification (ANZSRC)

• Earth Sciences

• Published_Internal

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2011-01-01T00:00:00

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