2009 Fiordland earthquake

The 2009 Fiordland earthquake struck the South Island of New Zealand with a magnitude of 7.8[1] at 9:22 pm (NZST) on 15 July. The earthquake was centred in the remote region of Fiordland, with the epicentre located 150 km (93 mi) west-north-west of Invercargill near Dusky Sound in Fiordland National Park, at a depth of 12 km (7.5 mi).[1][2] It is among the largest New Zealand earthquakes to occur, including the Culverden/Kaikoura earthquake in 2016 and the 1931 Hawke's Bay earthquake, which both had a magnitude of 7.8.[3][4]

2009 Fiordland earthquake
UTC time2009-07-15 09:22:29
ISC event15157724
USGS-ANSSComCat
Local date15 July 2009 (2009-07-15)
Local time9:22 pm (NZST)
Magnitude7.8 Mw
Depth12 kilometres (7 mi)
Epicenter45.721°S 166.643°E / -45.721; 166.643
Areas affectedNew Zealand
Max. intensityVII (Very strong) MMI
Tsunami17 cm (6.7 in)
Aftershocks>100
Casualties0

Earthquake

The main shock was a reverse fault (thrust), with the Indo-Australian Plate subducting beneath the Pacific Plate.[3] The earthquake lifted a large area of land around the epicenter approximately 1 metre.[5]

New Zealand's Institute of Geological and Nuclear Sciences (GNS Science) initially measured the earthquake at magnitude 6.6,[6] but later revised the magnitude to 7.8.[7]

The reported energy release was compared to "500 million tonnes of TNT,[and] 25,000 times more powerful than the atomic bomb dropped on Nagasaki in 1945".[8]

The quake twisted New Zealand's South Island, with Puysegur Point, on the Southwestern tip of the island, moving 30 cm closer to Australia (westward); Te Anau moved 10 cm, Bluff 3 cm and Dunedin 1 cm. It is also believed to have caused an increased stress in the southern, offshore part of the Alpine Fault.[9]

A considerable number of aftershocks were recorded.

Effects
NASA map showing epicentre of earthquake and its aftershocks

The earthquake was felt throughout the South Island, and in the lower North Island as far as New Plymouth. No injuries or fatalities were reported, and it caused only minor damage.[7] Power outages were experienced in several parts of the South Island.[10][11] Over 200 claims for damage have been listed with the Earthquake Commission, New Zealand's agency for earthquake compensation.[8]

Landslides in the Fiordland National Park near Dusky Sound cleared large tracts of forest.[8]

Tsunami

Tsunami warnings were issued soon after the earthquake by authorities in New Zealand and Australia, as well as the Pacific Tsunami Warning Center in Hawaii.[12] Civil defence officials in Southland also issued a 'potential tsunami' warning, stating their concerns about widely varying measurements of the earthquake.[10] Reacting to the Pacific warnings, about fifty residents and tourists on Lord Howe Island were evacuated, and in Sydney a theatre in Bondi Beach was evacuated, and residents told to keep away from the shore.[13] In the event, waves recorded along New Zealand's western coastline measured at one metre, peak to trough, in the Haast area.[3] (An amplitude of 17 cm)[14] The tsunami warnings were subsequently cancelled or reduced.[7]

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See also

References
  1. "Magnitude 7.8 – OFF WEST COAST OF THE SOUTH ISLAND, N.Z." USGS. 15 July 2009. Archived from the original on 12 August 2009. Retrieved 15 July 2009.
  2. "New Zealand Earthquake Report – Jul 15 2009 at 9:22 pm (NZST)". GeoNet. 15 July 2009. Archived from the original on 18 July 2009. Retrieved 16 July 2009.
  3. "Fiordland quake biggest for 80 years". GeoNet. Institute of Geological and Nuclear Sciences. 16 July 2009. Archived from the original on 26 July 2009. Retrieved 21 July 2009.
  4. NZPA (19 July 2009). "Weaker, more frequent Fiordland aftershocks". Stuff.co.nz. Archived from the original on 26 July 2009. Retrieved 21 July 2009.
  5. "Ground raised one metre by quake". Radio New Zealand. 18 July 2009. Archived from the original on 26 July 2009. Retrieved 21 July 2009.
  6. "Tsunami alert after NZ earthquake". BBC News. 15 July 2009. Retrieved 15 July 2009.
  7. NZPA, Fairfax (15 July 2009). "Fiordland quake measures 7.8". stuff.co.nz. Retrieved 15 July 2009.
  8. Yvonne Tahana (17 July 2009). "After-shocks continue in Southland". New Zealand Herald. Archived from the original on 26 July 2009. Retrieved 21 July 2009.
  9. Paul Gormon (22 July 2009). "Our Australian cousins just got closer". The Press. Fairfax Media. Archived from the original on 26 July 2009. Retrieved 21 July 2009.
  10. Dye, Stuart; NZPA (15 July 2009). "South Island quake prompts 'potential tsunami' warning". The New Zealand Herald. Retrieved 15 July 2009.
  11. "Quake strikes off New Zealand's Southland". Xinhua. 15 July 2009. Retrieved 15 July 2009.
  12. Beckford, Gyles (15 July 2009). "New Zealand quake sparks tsunami warnings". Reuters. Retrieved 15 July 2009.
  13. "Fiordland quake causes evacuation in Sydney". Television New Zealand News. 16 July 2009. Archived from the original on 26 July 2009. Retrieved 21 July 2009.
  14. "Tsunami Information Statement". West Coast and Alaska Tsunami Warning Center. 15 July 2009. Archived from the original on 26 July 2009. Retrieved 21 July 2009.

Further reading
  • Rogers, Anna (2013) [1996]. The Shaky Isles: New Zealand Earthquakes (2 ed.). Wellington: Grantham House. pp. 185, 186. ISBN 978-1-86934-119-0.
  • Wright, Matthew (2014). Living on shaky ground: The science and story behind New Zealand's earthquakes. Auckland: Random House (New Zealand). pp. 174, 175. ISBN 978-1-77553-688-8.
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