Neotectonic evidence for a crustal strain gradient on the central west WA margin  

Authors / CoAuthors

McPherson, A. | Clark, D.

Abstract

Compressional deformation is a common phase in the post-rift evolution of passive margins and rift systems. The central west Western Australian margin, between Geraldton and Karratha, provides an excellent example of strain partitioning between inverting passive margin crust and adjacent oceanic and continental crust. The distribution of contemporary seismicity in the region indicates a concentration of strain release within the basins diminishing eastward into the cratons. Very few data exist to quantify uplift or slip rates, however this pattern can be qualitatively demonstrated by tectonic landforms which indicate that the last century or so of seismicity is representative of patterns of Neogene and younger deformation. Pleistocene marine terraces on the western side of Cape Range indicate uplift rates of several tens of metres per million years, with similar deformation resulting in sub-aerial emergence of Miocene strata on Barrow Island and elsewhere. In the southern Carnarvon Basin, marine strandlines of unknown age are displaced by a few tens of metres, indicating uplift rates an order of magnitude lower than further west. Relief production rates in the western Yilgarn Craton are lower still - numerous scarps (e.g. Mt Narryer) appear to relate individually to <10 m of displacement across Neogene strata. The en echelon arrangement of such features distinguish them from those representing strain concentration in the craton proper, where scarps are isolated and typically <5 m high. Quantitative analysis of time-averaged deformation preserved in the aforementioned landforms, including study of scarp length as a proxy for earthquake magnitude, has the potential to provide useful constraint on seismic hazard assessments in a region which contains major population centres and nationally significant infrastructure.

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nonGeographicDataset

eCat Id

74786

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Keywords

• External PublicationAbstract

( Theme )

• continental margins

( Theme )

• deformation

( Theme )

• earthquakes

( Theme )

• geohazards

Australian and New Zealand Standard Research Classification (ANZSRC)

• Earth Sciences

• Published_Internal

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2013-01-01T00:00:00

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