Authors / CoAuthors
Clark, D. | McPherson, A. | Van Dissen, R.
Abstract
Australia boasts arguably the richest Late Neogene to Quaternary faulting record anywhere in the world's stable continental region (SCR) crust. Variation in Quaternary fault scarp length, vertical displacement, relation to other faults and topography justifies the division of the continent according to fault character. Six onshore 'neotectonic domains' are recognised, while an additional offshore domain is proposed by analogy with the eastern United States. Each domain relates to a distinct underlying crustal type and architecture, which can be broadly considered to represent cratonic, non-cratonic and extended crustal environments. In general, greater topographic expression associated with faults occurring in extended crust relative to non-extended crust suggests a higher rate of seismic activity in the former setting, consistent with observations worldwide. Using the same reasoning, non-cratonic crust might be expected to have a higher rate of seismic activity than cratonic crust. This distinction, together with the variance in fault character between domains, should be recognised in attempts to identify analogous systems elsewhere in the world. A common characteristic of large (paleo)earthquake occurrence in Australia appears to be temporal clustering. Periods of earthquake activity comprising a finite number of large events are separated by much longer periods of seismic quiescence. In several instances there is evidence for deformation at scales of several hundred kilometres switching on and off over the last several million years. What is not clear from the limited paleoseismological data available is whether successive active periods are comparable in terms of slip, number of events, magnitude of events, etc. Irrespective, this apparent bimodal recurrence behaviour poses problems for probabilistic seismic hazard assessment (PSHA) in that it implies that large earthquake recurrence for long return periods is not random (i.e. Poissonian). The points critical to understanding the hazard posed by SCR faults, and modelling this hazard probabilistically, become: 1) is the fault in question in the midst of an active period, or in a quiescent period; 2) how many large events might constitute an active period, and how many ruptures has the fault generated so far in its current active period (should it be in one); and 3) what is the mean recurrence interval in an active period, and what is the variability around this mean? Keywords: intra-plate, neotectonics, paleoseismology, temporal clustering
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nonGeographicDataset
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73046
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- External PublicationScientific Journal Paper
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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2012-01-01T00:00:00
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