Statistical properties and modelled duration of an intracontinental earthquake sequence: 2021 Mw 5.9 Woods Point earthquake, Australia

We investigate the 2021 moment magnitude (Mw) 5.9 Woods Point earthquake aftershock sequence (WPAS) in Victoria, Australia. WPAS Gutenberg-Richter b-values range from 0.76 to 1.07 and depend upon the earthquake magnitude type used (Mw vs Ml) and minimum completeness magnitude (Mc). The WPAS Modified Omori’s law p-value of 0.83~0.84 suggests slower aftershock decay rates, while the modelled duration of the WPAS (7.5 to 40.4 years) is consistent with estimated aftershock sequence durations in comparable continental intraplate settings. The high double-couple (>80%) of the mainshock and strong statistical fit of a sub-vertical plane to the aftershock cloud favour a structurally simple mainshock source fault. However, the delayed occurrence of the largest aftershocks (Ml 4.7, 4.2) and high proportion (~70%) of WPAS moment release sourced at distances > 1.5 km from the mainshock fault suggests aftershock activity on nearby structurally complex fault networks, as observed in other Australian sequences.