The March 30, 2025, M 7.0 Tonga earthquake resulted from reverse faulting west of the Tonga Trench in the South Pacific Ocean. Focal mechanism solutions indicate that rupture occurred on either a steeply dipping reverse fault or a shallowly dipping thrust fault. Given the depth and location, slip on the shallowly dipping thrust fault is more likely along the plate interface. At the earthquake's location, the Pacific plate subducts westward beneath the Australia plate at a velocity of about 73 mm/yr. 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.
The subduction zone surrounding Tonga and Fiji hosts large earthquakes regularly. Since 1900, nine other events of M 7 or larger have occurred within 250 km of the March 30 event. Many of these events pose a potential hazard due to the fact that they are shallow and can cause vertical displacement of the sea floor, leading to tsunamis. The proximity of these earthquakes to Tonga means that if a tsunami is generated, there is limited time to issue warnings before the tsunami wave reaches the coast.