The 2021 Mw 7.3 East Cape earthquake: Triggered Rupture in Complex Faulting Revealed by Multi‐Array Back‐projections

On 04 March 2021 the Mw 7.3 East Cape, New Zealand earthquake occurred at the southern end of the Kermadec Trench. The United States Geological Survey W-phase solution shows an unexpected focal mechanism compared to historical earthquakes. We combine earthquake back-projections of 4 arrays to image the kinematic process of the Mw 7.3 earthquake. Our results reveal a bilateral rupture predominantly propagating upward at a slow speed of 1 km/s and a triggered rupture at similar to 10 km, corresponding to the deep reverse faulting event at 70 km and a triggered shallow normal faulting event (similar to 20 km) resolved by previous subevent and finite fault inversions. The epicenter and a group of aftershocks are deeper than the bottom of the slab according to a regional tomography model. Such deep failure is possibly enabled by a delaminating lower crust of the Hikurangi plateau.