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Southwest Australia Seismic Network (SWAN): Recording Earthquakes in Australia’s Most Active Seismic Zone

Description: 

The geological structure of southwest Australia comprises a rich, complex record of Precambrian cratonization and Phanerozoic continental breakup. Despite the stable continental cratonic geologic history, over the past five decades the southwest of Western Australia has been the most seismically active region in continental Australia though the reason for this activity is not yet well understood. The Southwest Australia Seismic Network (SWAN) is a temporary broadband network of 27 stations, deployed since July 2020, designed to both record local earthquakes for seismic hazard applications and provide the opportunity to dramatically improve the rendering of 3-D seismic structure in the crust and mantle lithosphere. Such seismic data are essential for better characterization of the location, depth and attenuation of the regional earthquakes, and hence understanding of earthquake hazard and in addition, an improved understanding of the long tectonic history of the Australian continent.

Preliminary results from the deployment include a new machine learning based catalogue that has located 5000+ earthquakes and an ambient noise tomography model. Using ~20 months of continuous data recorded by SWAN stations, we have produced a 3-D Vs model of the crust and uppermost mantle with ambient noise tomography. Our images show distinct low-velocity anomalies beneath the Perth Basin and relatively high-velocity anomalies in the Yilgarn Craton separated by the N-S trending, inactive Darling Fault. In the center of the Perth Basin that is characterized by low velocities, we observe a small-scale high-velocity anomaly. Within the Yilgarn Craton, we detect a prominent structural contrast in the lower crust to the uppermost mantle along the boundary of the South West Terrane and the Youanmi Terrane. Included in the new catalogue, this array captured a significant earthquake swarm in the Arthur River region, located within the south-central part of the Yilgran craton, which began in early 2022 and to date has recorded 1850+ earthquakes, the largest with a MLa magnitude of 4.8 (MLv 5.1).

Session: Tectonics and Seismicity of Stable Continental Interiors [Poster]

Type: Poster

Date: 4/19/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Meghan S. Miller

Student Presenter: No

Invited Presentation: 

Authors