The 2 March 2016 Wharton Basin Mw7.8 earthquake: High stress drop north-south strike-slip rupture in the diffuse oceanic deformation zone between the Indian and Australian Plates

The diffuse deformation zone between the Indian and Australian plates has hosted numerous major and great earthquakes during the seismological record, including the 11 April 2012 M(w)8.6 event, the largest recorded intraplate earthquake. On 2 March 2016, an M(w)7.8 strike-slip faulting earthquake occurred in the northwestern Wharton Basin, in a region bracketed by north-south trending fracture zones with no previously recorded large event nearby. Despite the large magnitude, only minor source finiteness is evident in aftershock locations or resolvable from seismic wave processing including high-frequency P wave backprojections and Love wave directivity analysis. Our analyses indicate that the event ruptured bilaterally on a north-south trending fault over a length of up to 70km, with rupture speed of2km/s, and a total duration of similar to 35s. The estimated stress drop, similar to 20MPa, is high, comparable to estimates for other large events in this broad intraplate oceanic deformation zone.