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Large earthquake recurrence on the Willunga Fault, South Australia, revisited

Created 02/03/2026

Updated 02/03/2026

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In mid-2022 two paleoseismic trenches were excavated across the Willunga Fault, ~40 km south of Adelaide. Since the preliminary results of this investigation were presented at the 2022 AEES conference, dating results have allowed constraints to be placed on earthquake timing. Evidence is preserved for six surface-rupturing earthquakes within the last ca. 150 ka (E1-E6), associated with a slip rate estimated to be in the order of ~65-70 m/Myr. Two additional events are recognised between ca. 150 and 315 ka (E7-E8). A probability density plot indicates distinct peaks at recurrence intervals of ~17 and ~49 kyr. Single-event displacements on individual fault traces of ~0.5-1.7 m were measured, consistent with earthquake magnitudes of ~Mw 6.8, and rupture lengths of ~30 km. Stratigraphic relationships and geochronological constraints allow that displacement may have occurred concurrently on faults cutting the colluvial mantle, the bedrock/colluvium interface, and within a hanging wall flexural graben.

Vertical separation of pre-Cenozoic basement rocks across the Willunga Fault increases from north to south. The section of scarp studied here appears more geomorphically ‘youthful’ than further north. In the same amount of time that we recognise six surface rupture events at our site, only two events (consistent in time with E4 and E6) are recognised north of our site, at Mt Bold and McLaren Flat, respectively. A possible explanation is that the gradient in vertical separation between south and north is accommodated by segmented rupture, with the various segments bearing different slip rates, and different earthquake histories.

Presented at the Australian Earthquake Engineering Society (AEES) National Conference 2024

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Additional Info

Field Value
Title Large earthquake recurrence on the Willunga Fault, South Australia, revisited
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/dataset/35313c19-22aa-4fe5-8cfc-e6494b5ad8ec
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period 27/01/2026
Geospatial Coverage
Map data © OpenStreetMap contributors
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}
Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "Large earthquake recurrence on the Willunga Fault, South Australia, revisited". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/large-earthquake-recurrence-on-the-willunga-fault-south-australia-revisited