Kingdom of Tonga

Geographical situation and geophysical context

Tonga is an archipelago located in the South Pacific Ocean, east of Fiji and south of Samoa. It consists of more than 170 islands, with the main island being Tongatapu. Here are some key aspects of the geophysical context of Tonga:

  1. Tectonic Setting: Tonga lies within the Pacific Ring of Fire and is situated along the boundary of the Pacific Plate and the Australian Plate. It is part of the Tonga-Kermadec subduction zone, where the Pacific Plate is subducting beneath the Australian Plate. This subduction zone is known for its complex tectonic activity.
  2. Earthquakes: Tonga experiences frequent and often powerful earthquakes due to its location along the subduction zone. The region is known for hosting some of the deepest and largest earthquakes in the world. These earthquakes are a result of the intense tectonic forces and the release of accumulated stress along the plate boundary.
  3. Volcanic Activity: Tonga has a volcanic origin, and the archipelago includes both active and dormant volcanoes. The most well-known volcano in Tonga is Mount Tofua, located on the island of Tofua. Eruptions occur periodically, posing potential hazards such as ashfall, lava flows, and potential tsunamis.
  4. Oceanic Features: The waters surrounding Tonga include deep ocean trenches, such as the Tonga Trench, which is one of the deepest parts of the world’s oceans. These oceanic features contribute to the unique marine environment and oceanographic conditions around the islands.

Tonga seismic network, FSDN code : TG

  • HAP (Ha’apai), located on Ha’apai archipelago.
  • NFO (Niuafo’ou), located on Niuafo’ou island.
  • NTT (Niuatoputapu), located on Niuatoputapu island.
  • TPU (Foloha), located on Tongatapu island.
  • VAV (Vava’u), located on Vava’u island.

Currently, the Tonga seismic network is under re-design, most of the stations as been replaced by equipment provided by Geoscience Australia under the code “YC”, it consists of 8 stations with 4 broadband stations and 4 short period equipment.

National institutions

National observatories & agencies responsible for hazards monitoring and alert dissemination:

Tonga Geological Services – TGS

Mr. Taaniela KulaTGS Director
Mr Rennie VaiomoungaTGS Chief geologist

Tonga Meteorological Services – TMS

Mr. ‘Ofa FA’ANUNUTMS Director
Mr. Reginald HinganoTMS IT manager