The 2007 Gisborne earthquake occurred under the Pacific Ocean about 50 kilometres (31 mi) off the eastern coast of New Zealand's North Island at 8:55 pm NZDT on 20 December. With a moment magnitude of 6.7 and maximum Mercalli intensity of VII (Very Strong), the tremor affected the city of Gisborne and was felt widely throughout the country, from Auckland in the north to Dunedin in the south.[1]
 Damage outside Health 2000 Main Street | |
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| UTC time | 2007-12-20 07:55:15 |
|---|---|
| ISC event | 13293317 |
| USGS-ANSS | ComCat |
| Local date | 20 December 2007 |
| Local time | 8:55 pm NZDT (UTC+13) |
| Magnitude | 6.7 Mw[1] |
| Depth | 33 km (21 mi) |
| Epicentre | 38°53′S 178°32′E / 38.89°S 178.54°E |
| Areas affected | New Zealand |
| Max. intensity | MMI VII (Very strong) |
| Peak acceleration | 0.28 g |
| Casualties | 1 dead, 11 injured |
Tectonic setting
editNew Zealand lies along the boundary between the Indo-Australian plate and Pacific plate.
- In the South Island, most of the relative displacement between these plates is taken up along a single dextral (right lateral) strike-slip fault with a major reverse component, the Alpine Fault.
- In the North Island, displacement is mainly taken up along the Kermadec-Tonga subduction zone, although the remaining dextral strike-slip component is accommodated by the North Island Fault System. Subduction off the coast takes place at the Hikurangi Trough, which runs parallel to the East Coast of the North Island and is the southern extension from the Kermadec Trench, however earthquakes here occur less frequently.[2]
Earthquake
editThe earthquake occurred at 8:55 pm on 20 December 2007 off the coast of Gisborne, at a depth of about 40 kilometres. Shaking mostly affected Gisborne, but was felt throughout the country, from Auckland to Dunedin. Small appliances or furniture slipped or fell as far south as Wellington.[1]
Effects
editWhile the earthquake was initially reported to have caused no deaths, an elderly woman in Gisborne suffered a heart attack and died shortly after the quake.[3] A number of buildings in central Gisborne were damaged and had their roofs cave in. The central business district was closed off to allow building inspectors to assess buildings for damage; three buildings had collapsed. Gisborne's standby sewage system was activated. There were power outages immediately after the earthquake hit.[4] Temporary problems with phone, water and gas lines also occurred.[5][4] The town clock stopped at 8:55 pm.[6] The Earthquake Commission had received over 6,200 insurance claims costing a total of about $25 million, the biggest number since the 1987 Edgecumbe earthquake.[7] It was earlier estimated that the cost of damage caused by the earthquake could rise to $30 million.[8]
The National Crisis Management Centre was activated after the earthquake struck.[4] A state of emergency started on 21 December and lasted until 22 December.[9]
Liquefaction occurred near the Waipaoa River, and there was an increased activity in nearby mud volcanoes.[10]
See also
editReferences
edit- ^ a b c M 6.7, Gisborne, 20 December 2007 Archived 15 October 2018 at the Wayback Machine. GeoNet.
- ^ Mouslopoulou, V., Nicol, A., Little, T. A., & Walsh, J. J. (2007). Terminations of large strike-slip faults: an alternative model from New Zealand Archived 7 April 2022 at the Wayback Machine. Geological Society, London, Special Publications, 290 (1), pp 387–415.
- ^ One dead, up to 20 injured after huge quake Archived 26 January 2020 at the Wayback Machine, The New Zealand Herald, 21 December 2007.
- ^ a b c "Quake 6.8 magnitude hits east coast". 1 News. 21 December 2007. Archived from the original on 31 December 2007. Retrieved 29 July 2024.
- ^ "Woman's death blamed on NZ quake". Australia: ABC News. 21 December 2007. Retrieved 29 July 2024.
- ^ 'Rattled Gisborne residents pick up the pieces after quake', 3News. 21 December 2007. Retrieved 6 June 2009. Archived 10 June 2009.
- ^ Earthquake Commission Annual Report 2007–2008 (PDF) (Report). p. 6,7. Archived (PDF) from the original on 24 June 2024. Retrieved 31 July 2024.
- ^ The $30m shockwave Archived 23 December 2007 at the Wayback Machine, 22 December 2007
- ^ "City was lucky, earthquake seminar told". NZPA. 15 May 2008. Retrieved 6 October 2024.
- ^ "The Mw 6.6 Gisborne Earthquake of 2007: Preliminary Records and General Source Characterisation" (PDF). New Zealand Society for Earthquake Engineering. 4 December 2008.
External links
edit- New Zealand earthquake report – Magnitude 6.7, Thursday, 20 December 2007 at 8:55:17 pm (NZDT). GeoNet.
- M 6.6 – off the east coast of the North Island of New Zealand (U.S. Geological Survey)
- The International Seismological Centre has a bibliography and/or authoritative data for this event.