We investigate two intraplate earthquakes in a stable continental region of southwest Western Australia. Both small‐magnitude events occur in the top ∼1 km of crust and their epicenters are located with an accuracy of ∼100 m (1σ) using satellite Interferometric Synthetic Aperture Radar (InSAR). For the Mw 4.7 Katanning earthquake (10 October 2007) the average slip magnitude is 42 cm, over a rupture area of ∼1 km2. This implies a high static stress drop of 14–27 MPa, even for this very shallow earthquake, which may have important implications for regional seismic hazard assessment. The earthquake rupture extends from a depth of around 640 m to the surface, making it a rarely observed intraplate, surface‐rupturing event. Using InSAR observations, we estimate the coseismic slip distribution of the shallow earthquake, such estimates being rarely available for small magnitude events. For the Mw 4.4 composite Kalannie earthquake sequence (21–22 September 2005), we use a long‐term time series analysis technique to improve the measurement of the co‐seismic signal, which is a maximum of 27 mm in the line‐of‐sight direction. Double difference seismic analysis shows some relocated cluster seismicity which corresponds in timing, location, and source parameters to the InSAR‐observed deformation. This earthquake is the smallest magnitude seismic event to have been investigated using InSAR and demonstrates the capability of the technique to provide important constraints on small‐magnitude coseismic events. The shallow depth of both these events adds weight to the suggestion that earthquakes associated with tectonic processes in this area of Western Australia often initiate in the upper 1 km of crust.

We assessed the accuracy of earthquake source parameters inverted from simulated Interferometric Synthetic Aperture Radar (InSAR) data. Using focal mechanisms of Australian earthquakes (1959 to the present), we simulated synthetic two‐pass InSAR observations with realistic spatial noise derived from the characteristics of actual ERS‐2 and ENVISAT InSAR data observed over Australia. The precision of two‐pass satellite SAR interferometry with ERS‐2 and ENVISAT SAR data in the Australian region can approach ±2 mm (1σ) and is routinely at the ±4 mm level. The use of spatially correlated observational weights has minimal impact on the accuracy of earthquake source parameters inverted from InSAR data. In most cases single geometry (i.e., ascending or descending) InSAR observations can be used to accurately determine earthquake source parameters, although typically a combined geometry reduces the source parameter uncertainties by a factor of 1.5. In general, earthquakes of magnitude <4.8 are unlikely to be observable by InSAR although very shallow events would be detectable. InSAR is insensitive to magnitude 6.2 earthquakes deeper than 10 km, and magnitude 5.5 deeper than 6 km. For earthquake magnitudes ≥5.8 (average depth 6.5 km) we could estimate the epicenter of the rupture with an average accuracy of 0.25 km, depth to within 0.5 km and the fault orientation to better than 2°. Our findings, based on simulated Australian earthquakes, are representative of typical intraplate earthquakes and would be valid in many other regions. To date no actual earthquakes have been observed by InSAR in Australia.

No abstract

This paper describes the purpose, design and implementation of a new regional-scale geodetic network that has been installed in the Surat Basin, Queensland, and completed in November 2014. The network incorporates 65 survey marks and 40 radar corner reflectors to enable the combination of Global Navigation Satellite System measurements with remotely sensed surface deformation maps derived using the Interferometric Synthetic Aperture Radar technique. The combination of these geodetic techniques in this region will bring an enhanced understanding of how resource extraction affects the ground surface.

We present a comparison of atmospheric precipitable water vapor (PWV) derived from ground-based global positioning system (GPS) receiver with traditional radiosonde measurement and very long baseline interferometry (VLBI) technique for a five-year period (2008–2012) using Australian GPS stations. These stations were selectively chosen to provide a representative regional distribution of sites while ensuring conventional meteorological observations were available. Good agreement of PWV estimates was found between GPS and VLBI comparison with a mean difference of less than 1 mm and standard deviation of 3.5 mm and a mean difference and standard deviation of 0.1 mm and 4.0 mm, respectively, between GPS and radiosonde measurements. Systematic errors have also been discovered during the course of this study, which highlights the benefit of using GPS as a supplementary atmospheric PWV sensor and calibration system. The selected eight GPS sites sample different climates across Australia covering an area of approximately 30° NS/EW. It has also shown that the magnitude and variation of PWV estimates depend on the amount of moisture in the atmosphere, which is a function of season, topography, and other regional climate conditions.