Authors / CoAuthors
Clark, D.J. | Rawson, A.
Abstract
A structural transect along a ridge entering Wheeny Gap from the west provides important insight into the nature of faults comprising the Lapstone Structural Complex (LSC). Sheared sandstone outcropping along the ridge east of the Kurrajong fault scarp suggests that the Kurrajong Fault is a steeply east-dipping reverse-fault, in accordance with the interpretation of seismic profiles further to the south. A previously unrecognised west-dipping reverse fault (Wheeny Gap Fault) with at least several tens of metres of displacement was observed in a cliff face on the northern side of Wheeny Gap, several hundred metres east of the Kurrajong Fault. Relatively recent activity is suggested on the Wheeny Gap Fault as it laterally displaces the cliff face formed during the passage of a knickpoint relating to initial relief generation across the Lapstone Monocline up Wheeny Creek. Earthquake hypocentres recorded over the last several decades occur predominantly at depth to the west, and have been used to suggest the presence of a blind west-dipping reverse fault, into which the Kurrajong and Wheeny Gap faults must link at depth. We present an evolutionary model for the LSC based upon this architecture which reconciles evidence for late Cenozoic uplift across the LSC and the observation that the Rickabys Creek Gravels overlie shale on the Cumberland Plain and sandstone on the Lapstone Monocline. This model suggests that the findings of a major seismic hazard assessment of the Sydney Basin, which concludes that magnitude MW7.0 and greater earthquake events might be expected on the LSC on average every 15-30 ka, should be treated with caution. This expectation of regular recurrence must be tempered by the possibility that a large part of the relief relating to the complex might have formed in the late Miocene or earlier, and the evidence from other Australian intraplate faults suggesting that large earthquake occurrence is markedly temporally clustered.
Product Type
nonGeographicDataset
eCat Id
65975
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
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Keywords
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- GA PublicationRecord
- ( Theme )
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- drainage
- ( Theme )
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- earthquakes
- ( Theme )
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- geohazards
- ( Theme )
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- geomorphology
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- AU-NSW
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
Publication Date
2008-01-01T00:00:00
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geoscientificInformation
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Record
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[-34.4, -33.25, 150.3, 151.4]
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Spatial Resolution
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