On January 15, 2022, an explosive and violent eruption occurred on the undersea volcano of Hunga Haapai Island in the southwest Pacific Ocean, attracting global attention. The Hunga Haapai Island is located in the Tonga-Kermadec subduction zone. Based on the previous research results, this paper makes a preliminary analysis of the geological structures, seismic and volcanic distribution of the Tonga-Kermadec subduction zone, and finds that (1) The forearc area of the Tonga-Kermadec subduction zone mainly develops large-scale normal faults; (2) The subduction of the Louisville Ridge Seamount Chain divides the Tonga-Kermadec subduction zone into the Tonga subduction zone in the north and the Kermadec subduction zone in the south. The plate aggregation rate along the Tonga subduction zone is 67-84 mm/a, and the plate aggregation rate along the Kermadec subduction zone is 41~58 mm/a. The difference in plate aggregation speed cause differences in the current subduction depth between the Tonga subduction zone and the Kermadec subduction zone; (3) North of the Louisville Ridge Seamount Chain, the thickness of the overburden sediment in the Pacific Plate is less than 0.4 km, and it reaches about 1 km on the south side. Differences in sediment thickness cause differences in earthquake generating capacity in the Tonga subduction zone and the Kermadec subduction zone. These understandings are of great significance for studying the volcanic eruption mechanism, the cause mechanism of major earthquakes and disaster risk in the subduction zone.

Tonga Volcano  /  volcanic eruption  /  subduction zone geological structures  /  subduction earthquake