2006 Tonga earthquake
Coordinates: The 2006 Tonga earthquake occurred on 4 May 2006 at 04:26 local time (3 May 2006 at 15:26 UTC). There were no reports of death or injury. With a strength of 7.9 it was the strongest quake since the 28 March 2005 Sumatra earthquake following from the infamous 2004 Indian Ocean earthquake (although some others came close) (USGS data).
The United States Geological Survey assigned the quake a preliminary magnitude estimate of 7.8 on the Moment magnitude scale, which was later increased to 8.0, and at the end settled on 7.9. The earthquake had its epicenter 165 km south of Neiafu, Tonga, or 2145 km northnortheast of Auckland, New Zealand. Since the earthquake occurred underwater, tsunami warnings were issued, but then lifted. Small, barely noticed aftershocks occurred at 06:56 and 08:28. In addition, the next night, around local midnight, an aftershock of magnitude 6. Such a relatively strong shock after such a long time is a quite exceptional occurrence. On the other hand, earthquakes happen so regularly in this area that the distinction between aftershock and next shock may blur.
CNN initially reported that the quake was believed to have been 8.0 on the Richter scale, but as news from Fiji continued, the measurement changed to 7.8 on the Richter scale. CNN and BBC reports showed that the town of Gisborne, New Zealand was being evacuated. Civil Defence in New Zealand had issued no statements, and there was no information inside New Zealand about Gisborne being evacuated. As people started receiving phone calls from friends and family in the United States and Britain, they did not know what to do. The National Oceanic and Atmospheric Administration's Pacific Tsunami Warning Center in Hawaii issued a warning 17 minutes after the earthquake for coastal areas around the Pacific. An hour later, the center downgraded the warning to only the region within 600 miles of the epicenter, and an hour after that, it canceled the alert. No one died from this, but there were a couple of injuries.
In summary, with regards to the earthquake magnitude, the event caused very limited damage. The previous large earthquake in Tonga, in 1977, was of inferior magnitude but resulted in more severe damage. A likely cause is that the 2006 quake generated other frequencies that only resulted in resonance in small items. It was striking to see, especially in the supermarkets, all the cans and bottles which contained fluids turned upside down or fallen to the ground, while the bigger items or those containing dry goods were largely unaffected (see a.o. Tonga online news). There was very little damage reported in Tonga apart from pictures fallen from the walls or items tumbled down from cupboards and shelves.
- The century old, Catholic church in Lapaha got cracks in the cement of its tower and several stones fell down, leaving the steeple in a somewhat unstable position.
- The tower of a 60 year old church, of the Free church of Tonga in Veitongo, collapsed, the steeple came down and several walls cracked beyond repair. As in Lapaha, the faithful continued their services inside.
- During the quake a Korean business man jumped in panic from his second floor hotel room and got hurt in the fall. He was brought to the hospital where he had to wait a long time for any help as power was off and most staff off duty (as that day was a public holiday).
- The American wharf in Nukuʻalofa got some cracks in addition to those caused by the 1977 earthquake.
- A ship, sunk in 1949 near Toula, Vavaʻu apparently burst open and its load of copra came floating to the ocean surface.
- A landslide occurred at Hunga island in Vavaʻu, when the ground at a steep cliff along the shore began gliding into the sea.
- In Haʻapai, the islands closest to the epicentre, the wharf was damaged and a number of water-pipes and telephone lines were broken. Niuʻui hospital suffered severe damage beyond repair.
- Chang, Kenneth (4 May 2006). "Quake Causes Tsunami Alert, But No Damage". New York Times. Retrieved 22 May 2013.
- Pacific Tsunami Warning Center
- U.S. Geological Survey, National Earthquake Information Center
- Tongan online news
- Global Disaster Alert and Coordination System event report.