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A tale of two seisms Down Under: 23 March 2012 Mw 5.4 Ernabella and 9 June 2013 Mw 5.6 Mulga Park

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Created 13/01/2025

Updated 13/01/2025

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On 23 March 2012 a MW 5.4 intraplate earthquake occurred in the eastern Musgrave Ranges of north-central South Australia, near the community of Ernabella (Pukatja). This was the largest earthquake recorded on mainland Australia in the past 15 years and resulted in the formation of a 1.6 km-long surface deformation zone that included reverse fault scarps with a maximum vertical displacement of ~0.5 m (average ~0.1 m), extensive ground cracking, and numerous rock falls. Fifteen months later, on 09 June 2013 a MW 5.6 earthquake (the Mulga Park earthquake) occurred ~15-20 km northwest of the 2012 rupture. The P-axes of the focal mechanisms constructed for both events indicate northeast-oriented horizontal compressive stress. However, the focal mechanism for the Mulga Park earthquake suggests strike-slip failure, with a sub-vertical northerly-trending nodal plane favoured as the failure plane, in contrast to the thrust mechanism for the 2012 event. Despite being felt more widely than the 2012 event, ground cracking and minor dune settlement were the only surface expressions relating to the Mulga Park earthquake. No vertical displacements were evident, nor were patterns indicative of a significant lateral displacement. An 18 km long north to north east trending arcuate band of moderate to high cracking density was mapped parallel to the surface trace of the Woodroffe Thrust, a major crust-penetrating fault system. A lobe of high-density cracking ~5km long, coincident with the calculated epicentral location, extended to the north from the centre of the main arc. We speculate that the rupture progressed to the south beneath the northern high-density lobe (consistent with the dimensions expected from new scaling relations), and that the larger arcuate band of cracking might relate to positive interference resulting from reflection of energy from the Woodroffe Thrust interface. Both events provide new insight into the rupture behaviour of faults in non-extended cratonic crust.

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Title A tale of two seisms Down Under: 23 March 2012 Mw 5.4 Ernabella and 9 June 2013 Mw 5.6 Mulga Park
Language eng
Licence notspecified
Landing Page https://devweb.dga.links.com.au/data/dataset/af2039d7-e526-48ed-9bd2-8ae5492b4015
Contact Point
Geoscience Australia
clientservices@ga.gov.au
Reference Period 20/04/2018
Geospatial Coverage http://www.ga.gov.au/place-names/PlaceDetails.jsp?submit1=GA1
Data Portal data.gov.au

Data Source

This dataset was originally found on data.gov.au "A tale of two seisms Down Under: 23 March 2012 Mw 5.4 Ernabella and 9 June 2013 Mw 5.6 Mulga Park". Please visit the source to access the original metadata of the dataset:
https://devweb.dga.links.com.au/data/dataset/a-tale-of-two-seisms-down-under-23-march-2012-mw-5-4-ernabella-and-9-june-2013-mw-5-6-mulga-par