The 2009 Tonga earthquake occurred with a moment magnitude of 7.6 off the coast of Tonga on March 19 at 18:17:41 UTC. It had a depth of around 34 kilometres (21 mi). A tsunami warning was issued in the aftermath of the earthquake, although this was later cancelled. It was followed a short while later by an aftershock earthquake that had a magnitude of 5.3. Two more aftershocks followed on March 20 (UTC), with magnitudes of 5.4 and 5.0 Mw, then another magnitude 5.0 aftershock on March 21, totalling four aftershocks above magnitude 5. The quake occurred approximately 220 kilometres (140 mi) to the southeast of Nuku'alofa, the capital of Tonga, and initial reports suggest that there have been no injuries or significant damage. The earthquake was felt as far away as New Zealand's North Island, over 3,000 kilometres (1,900 mi) away.
The earthquake occurred four days after the beginning of a major underseavolcanic eruption near Hunga Tonga. There has been no confirmation yet of a direct link between the volcanic eruption and earthquake, but Ken Hudnut, a geophysicist for the United States Geological Survey, stated that "it seems suggestive at this point". Keleti Mafi, the Tongan government's chief seismologist, has suggested that the earthquake is likely to have a direct impact on the volcanic eruption, stating that the "strength of the earthquake could crack the volcano's (undersea) vent and allow more magma to be ejected".