M 7.3 - 205 km ESE of Neiafu, Tonga

  • 2022-11-11 10:48:46 (UTC)
  • 19.288°S 172.147°W
  • 37.0 km depth

Tectonic Summary

The November 11, 2022, M 7.3 Tonga earthquake occurred as a result of reverse faulting within the outer rise of the Pacific plate, approximately 75 km east of the Tonga Trench. Focal mechanism solutions indicate that rupture occurred on reverse fault dipping moderately either to the west or to the east-southeast. To the west of this earthquake, the Pacific plate subducts beneath the Australian plate at about 77 mm/yr. Although earthquakes in the outer rise are most commonly extensional, this compressional event may have occurred somewhat deeper within the Pacific plate, in the zone of expected compression induced by the bending of the Pacific plate as it subducts.

The broad-scale Australia-Pacific plate boundary is one of the most active in the world. Earthquakes occur on the thrust fault boundary between the Australia and Pacific plates, within the Pacific plate, and within and on the boundaries of the small microplates that together comprise the eastern edge of the Australia plate.

While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area. Modeling of this earthquake assuming the west-dipping fault plane implies dimensions of about 50x35 km, predominantly downdip of the hypocenter.

The subduction zone surrounding Tonga and Fiji hosts large earthquakes quite regularly. Over the preceding 40 years, three other events of M 7 or larger have occurred within 250 km of the November 11 event. The largest was a M 8.0 earthquake in May 2006, about 200 km to the southwest of the November 11 event, within the downgoing Pacific plate.

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