M 7.0 - Kermadec Islands region

Tectonic Summary

The March 16, 2023 M 7.0 earthquake near the Kermadec Islands occurred as a result of shallow faulting near the Kermadec Trench where the Pacific plate begins its descent into the mantle beneath the eastern edge of the Australia plate. Focal mechanism solutions indicate that rupture occurred on either a shallowly dipping strike-slip fault striking to the east, or a nearly vertical dip-slip fault striking to the southwest. At the location of this earthquake, the Pacific plate is converging with Australia in a westward direction at a velocity of about 61 mm/yr. The preliminary mechanism and depth of the event suggest it ruptured a fault within the subducting oceanic lithosphere of the Pacific plate, as it bends to subduct beneath the Australia plate.

The March 16th earthquake struck in an oceanic region with few nearby populations, approximately 600 km south of Tonga and 600 km north of New Zealand. This region of the Tonga-Kermadec subduction zone experiences high levels of seismic activity, with six earthquakes of M 7.0 or greater within 250 km in the preceding 20 years. This includes M 7.4 and 8.1 earthquakes that occurred 107 minutes apart on March 4, 2021, about 100 km west of the 2023 event.