M 7.1 - Kermadec Islands, New Zealand

  • 2023-04-24 00:41:55 (UTC)
  • 29.957°S 177.839°W
  • 46.8 km depth

Tectonic Summary

The April 24, 2023 M 7.1 earthquake near the Kermadec Islands occurred as a result of shallow reverse faulting in the Tonga-Kermadec subduction zone. The depth, location, and faulting mechanism of the earthquake indicate that the earthquake occurred on either an east or west dipping reverse fault at or near the plate boundary interface. At this location, the Pacific plate subducts westward beneath the Australia plate at a rate of approximately 61 mm/yr.

Although earthquakes are often plotted as points on a map, they occur on faults and rupture a finite area. Preliminary finite fault models indicate that the April 24 earthquake ruptured a section of fault 45 km long and 40 km wide. The preferred finite fault model suggests that the ruptured fault dips to the west into the subduction zone.

The April 24 earthquake is an aftershock of a M 8.1 earthquake that occurred two years prior on March 4, 2021. That 2021 earthquake was preceded 1.5 hours by a M 7.4 foreshock, and it has produced an additional M 7.0 aftershock that occurred on March 16, 2023. Overall, the Tonga-Kermadec subduction zone is very seismically active, and 18 other earthquakes of M 7.0 or larger have occurred with 250 km of the April 24, 2023 earthquake since 1970. Despite the frequent occurrence of large earthquakes in this region, there are rarely human impacts given the remote location of the earthquakes.

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