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John Dawson, Geoscience Australia (Australia)
Phil Cummins, Geoscience Australia (Australia)
Paul Tregoning, Australian National University (Australia)
Mark Leonard, Geoscience Australia (Australia)
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We investigate shallow seismicity in a stable continental region of southwest Western Australia with space-based Interferometric Synthetic Aperture Radar (InSAR). We observe surface deformation associated with two small co-seismic events including the Mw 4.4 (composite) Kalannie earthquake sequence (Sept. 2005) and the Mw 4.8 Katanning earthquake (Oct. 2007). For the Kalannie earthquake sequence (depth 1 km) we use a long-term time series analysis technique to improve the observation of the co-seismic signal, which is a maximum of 27 mm (line-of-sight). For the Katanning earthquake we find surface deformation of up to 216 mm (line-of-sight) and conclude that the rupture fault extends from a depth of around 650 m to the surface. For both earthquakes, despite their shallowness, the resulting co-seismic deformation is well modelled using elastic dislocation theory. They are the most precisely located earthquakes in the Australian earthquake catalog, with the precision of the position and depth, estimated to be better than 100 m (1 sigma). Their shallowness adds weight to the suggestion that earthquakes associated with tectonic processes in this area of Western Australia often initiate in the shallow upper crust.
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