2006 Tonga earthquake
Encyclopedia
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).
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. No tsunami alert sirens could be heard, nor was there any information on what to do, so people naturally assumed the worst. Many people headed inland, towards higher ground, only to find out minutes later that the alert had been cancelled. No one died from this, but there were a couple of injuries.
Tonga
Tonga, officially the Kingdom of Tonga , is a state and an archipelago in the South Pacific Ocean, comprising 176 islands scattered over of ocean in the South Pacific...
earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
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
2005 Sumatra earthquake
The 2005 Sumatra earthquake, referred to as the Nias Earthquake by the scientific community, was a major earthquake on 28 March 2005, located off the west coast of northern Sumatra, Indonesia. Approximately 1300 people were killed by the earthquake, mostly on the island of Nias...
following from the infamous 2004 Indian Ocean earthquake
2004 Indian Ocean earthquake
The 2004 Indian Ocean earthquake was an undersea megathrust earthquake that occurred at 00:58:53 UTC on Sunday, December 26, 2004, with an epicentre off the west coast of Sumatra, Indonesia. The quake itself is known by the scientific community as the Sumatra-Andaman earthquake...
(although some others came close) (USGS data).
Summary
The United States Geological SurveyUnited States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...
assigned the quake a preliminary magnitude estimate of 7.8 on the Moment magnitude scale
Moment magnitude scale
The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...
, which was later increased to 8.0, and at the end settled on 7.9. The earthquake had its epicenter
Epicenter
The epicenter or epicentre is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates...
165 km south of Neiafu, Tonga
Tonga
Tonga, officially the Kingdom of Tonga , is a state and an archipelago in the South Pacific Ocean, comprising 176 islands scattered over of ocean in the South Pacific...
, or 2145 km northnortheast of Auckland
Auckland
The Auckland metropolitan area , in the North Island of New Zealand, is the largest and most populous urban area in the country with residents, percent of the country's population. Auckland also has the largest Polynesian population of any city in the world...
, New Zealand. Since the earthquake occurred underwater, tsunami warnings
Tsunami warning system
A Tsunami warning system is used to detect tsunamis in advance and issue warnings to prevent loss of life and damage. It consists of two equally important components: a network of sensors to detect tsunamis and a communications infrastructure to issue timely alarms to permit evacuation of coastal...
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
CNN
Cable News Network is a U.S. cable news channel founded in 1980 by Ted Turner. Upon its launch, CNN was the first channel to provide 24-hour television news coverage, and the first all-news television channel in the United States...
initially reported that the quake was believed to have been 8.0 on the Richter scale, but as news from Fiji
Fiji
Fiji , officially the Republic of Fiji , is an island nation in Melanesia in the South Pacific Ocean about northeast of New Zealand's North Island...
continued, the measurement changed to 7.8 on the Richter scale. CNN and BBC
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
reports showed that the town of Gisborne
Gisborne, New Zealand
-Economy:The harbour was host to many ships in the past and had developed as a river port to provide a more secure location for shipping compared with the open roadstead of Poverty Bay which can be exposed to southerly swells. A meat works was sited beside the harbour and meat and wool was shipped...
, 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
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, they did not know what to do. No tsunami alert sirens could be heard, nor was there any information on what to do, so people naturally assumed the worst. Many people headed inland, towards higher ground, only to find out minutes later that the alert had been cancelled. No one died from this, but there were a couple of injuries.
Damage
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 NukualofaNukuʻalofaNukualofa is the capital of the Kingdom of Tonga. It is located on the north coast of the island of Tongatapu, in the southern most island group of Tonga.-Mythological origins:...
got some cracks in addition to those caused by the 1977 earthquake. - A ship, sunk in 1949 near ToulaToulaToula may refer to:* Toula, Lebanon, a village in the Northern mountains of Lebanon in the district Qada of Batroun* Toula, Lebanon, a village in the Northern mountains of Lebanon in the district Qada of Zgharta...
, VavauVava'uVavau is an island chain of one large island and 40 smaller ones in Tonga. According to tradition Maui fished both Tongatapu and Vavau but put a little more effort into the former. Vavau rises 204 meters above sea level...
apparently burst open and its load of copraCopraCopra is the dried meat, or kernel, of the coconut. Coconut oil extracted from it has made copra an important agricultural commodity for many coconut-producing countries. It also yields coconut cake which is mainly used as feed for livestock.-Production:...
came floating to the ocean surface. - A landslideLandslideA landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...
occurred at Hunga island in Vavau, when the ground at a steep cliff along the shore began gliding into the sea. - In HaapaiHa'apaiHaapai is a group of islands, islets, reefs and shoals in the central part of the Kingdom of Tonga, with the Tongatapu group to the south and the Vavau group to the north. Seventeen of the Haapai islands are populated....
, the islands closest to the epicentre, the wharf was damaged and a number of water-pipes and telephone lines were broken. Niuui hospital suffered severe damage beyond repair.
External links
- BBC
- MSN
- Pacific Tsunami Warning Center
- U.S. Geological Survey, National Earthquake Information Center
- Tongan online news
- Global Disaster Alert and Coordination System event report.