Source and Attenuation Properties of the 2012 Moe, Southeastern Australia, Earthquake Sequence

Abstract

The 19 June 2012 local magnitude ML 5.4 (\u2060Mw 5.1) Moe earthquake, which occurred within the Australian stable continental region, was the largest seismic event for the state of Victoria, for more than 30 yr. Seismic networks in the southeast Australian region yielded many high‐quality recordings of the moderate‐magnitude earthquake mainshock and its largest aftershock (\u2060ML 4.4 and Mw 4.3) at a range of distances from the epicenter. The source and attenuation characteristics of the earthquake sequence are analyzed. Almost 15,000 felt reports were received following the mainshock, and its ground motions tripped a number of coal‐fired power generators in the region amounting to the loss of, approximately, 1955 MW of generation capacity. The attenuation of macroseismic intensities is shown to mimic the attenuation shape of eastern North America (ENA) models but requires an interevent bias to reduce predicted intensities. Furthermore, instrumental ground‐motion recordings are compared to ground‐motion models (GMMs) considered applicable for the southeastern Australian (SEA) region. Some GMMs developed for ENA and SEA provide reasonable estimates of the recorded ground motions of spectral acceleration within epicentral distances of, approximately, 100 km. The mean Next Generation Attenuation‐East GMM, recently developed for stable ENA, performs relatively poorly for the 2012 Moe earthquake sequence, particularly, for short‐period accelerations. These observations will help inform future seismic hazard assessments for eastern Australia.