The 1843 Whanganui earthquake occurred on 8 July at 16:45 local time with an estimated magnitude of 7.5 on the scale. The maximum perceived intensity was IX (''Violent'') on the Mercalli intensity scale, and possibly reaching X (''Extreme''). The

epicentre The epicenter, epicentre () or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates. Surface damage Before the instrumental pe ...

is estimated to have been within a zone extending 50 km northeast from

Whanganui Whanganui (; ), also spelled Wanganui, is a city in the Manawatū-Whanganui region of New Zealand. The city is located on the west coast of the North Island at the mouth of the Whanganui River, New Zealand's longest navigable waterway. Whang ...

towards

Taihape Taihape is in the Rangitikei District of the North Island of New Zealand. It serves a large rural community. State Highway 1, which runs North to South through the centre of the North Island, passes through the town. History and culture Early ...

GNS Science GNS Science ( mi, Te Pū Ao), officially registered as the Institute of Geological and Nuclear Sciences Limited, is a New Zealand Crown Research Institute. It focuses on geology, geophysics (including seismology and volcanology), and nuclear sc ...

has this earthquake catalogued and places the epicentre 35 km east of Taihape, near the border of

Hawke's Bay Hawke's Bay ( mi, Te Matau-a-Māui) is a local government region on the east coast of New Zealand's North Island. The region's name derives from Hawke Bay, which was named by Captain James Cook in honour of Admiral Edward Hawke. The region i ...

. This was the first earthquake in New Zealand over magnitude 7 for which written records exist, and the first for which deaths were recorded.

Tectonic setting

New Zealand lies along the boundary between the

Australian Australian(s) may refer to: Australia * Australia, a country * Australians, citizens of the Commonwealth of Australia ** European Australians ** Anglo-Celtic Australians, Australians descended principally from British colonists ** Aboriginal A ...

and Pacific Plates. In 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 The Alpine Fault is a geological fault that runs almost the entire length of New Zealand's South Island (c. 480 km) and forms the boundary between the Pacific Plate and the Indo-Australian Plate. The Southern Alps have been uplifted on the f ...

. In North Island the displacement is mainly taken up along the Kermadec subduction zone, although the remaining dextral strike-slip component of the relative plate motion is accommodated by the North Island Fault System (NIFS). A group of dextral strike-slip structures, known as the Marlborough Fault System, transfer displacement between the mainly

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and convergent type plate boundaries in a complex zone at the northern end of South Island. The presumed epicentre of the 1843 earthquake is not, however, associated with any known fault.

Earthquake characteristics

The shock was felt over much of North Island and was reported as lasting for three minutes near

Mokoia Mokoia is a small settlement in south Taranaki, in the western North Island of New Zealand. It is located on State Highway 3, to the east of Hāwera and about 17 km northwest of Patea. History and culture Mokoia is close to the site of ...

. A magnitude of 7.5 was estimated from the extent of the area that was subject to a shaking level of at least VIII (''Severe''). At least ten aftershocks were reported on the same day as the mainshock and further shocks were reported until January 1845.

Damage

Damage in the Whanganui area reached IX–X on the Mercalli intensity scale. Many houses were damaged, and a brick church at Putiki was destroyed. There was extensive lateral spreading of the terrace margin to the

Whanganui River The Whanganui River is a major river in the North Island of New Zealand. It is the country's third-longest river, and has special status owing to its importance to the region's Māori people. In March 2017 it became the world's second natur ...

, and a section of Shakespeare Cliff fell into the river. Two people were killed when their house was swept away by one of the landslides caused by the earthquake.A tremulous motion, Barry Hawkins
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References

{{DEFAULTSORT:1843 Wanganui Earthquake Earthquakes in New Zealand History of Manawatū-Whanganui

Wanganui Whanganui (; ), also spelled Wanganui, is a city in the Manawatū-Whanganui region of New Zealand. The city is located on the west coast of the North Island at the mouth of the Whanganui River, New Zealand's longest navigable waterway. Whang ...

1843 in New Zealand July 1843 events 1843 disasters in New Zealand

Tectonic setting

Earthquake characteristics

Damage

See also

References