1843 Wanganui earthquake
Encyclopedia
The 1843 Wanganui earthquake occurred on July 8, 1843 with an epicenter
near Wanganui
, North Island
New Zealand
. This was the first earthquake
in New Zealand over magnitude 7 for which written records exist.
and Pacific Plate
s. 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
. 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 transform
and convergent type plate boundaries
in a complex zone at the northern end of South Island. The presumed epicenter of the 1843 earthquake is not, however, associated with any known fault.
. Many houses were damaged, and a brick church at Pūtiki was destroyed. There was extensive lateral spreading of the terrace margin to the Whanganui River
, 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.
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...
near Wanganui
Wanganui
Whanganui , also spelled Wanganui, is an urban area and district on the west coast of the North Island of New Zealand. It is part of the Manawatu-Wanganui region....
, North Island
North Island
The North Island is one of the two main islands of New Zealand, separated from the much less populous South Island by Cook Strait. The island is in area, making it the world's 14th-largest island...
New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. This was the first 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...
in New Zealand over magnitude 7 for which written records exist.
Tectonic setting
New Zealand lies along the boundary between the AustralianIndo-Australian Plate
The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and surrounding ocean, and extends northwest to include the Indian subcontinent and adjacent waters...
and Pacific Plate
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic plate....
s. In South Island
South Island
The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south and east by the Pacific Ocean...
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
Alpine Fault
The Alpine Fault is a geological fault, more specifically known as a right-lateral strike-slip fault, that runs almost the entire length of New Zealand's South Island. It forms a transform boundary between the Pacific Plate and the Indo-Australian Plate. Earthquakes along the fault, and the...
. In North Island
North Island
The North Island is one of the two main islands of New Zealand, separated from the much less populous South Island by Cook Strait. The island is in area, making it the world's 14th-largest island...
the displacement is mainly taken up along the Kermadec subduction zone
Kermadec Trench
The Kermadec trench is one of Earth's deepest oceanic trenches, reaching a depth of . Formed by the subduction of the Pacific Plate under the Indo-Australian Plate, it runs over a thousand kilometres parallel with and to the east of the Kermadec Ridge and island arc, from near the northeastern tip...
, although the remaining dextral strike-slip component of the relative plate motion is accommodated by the North Island Fault System
North Island Fault System
The North Island Fault System or North Island Dextral Fault Belt is a set of southwest-northeast trending seismically-active faults in the North Island of New Zealand that carry most of the dextral strike-slip component of the oblique convergence of the Pacific Plate with the Australian Plate...
(NIFS). A group of dextral strike-slip structures, known as the Marlborough Fault System
Marlborough Fault System
The Marlborough Fault System is a set of four large dextral strike-slip faults and other related structures in the northern part of South Island, New Zealand, which transfer displacement between the mainly transform plate boundary of the Alpine fault and the mainly destructive boundary of the...
, transfer displacement between the mainly transform
Transform fault
A transform fault or transform boundary, also known as conservative plate boundary since these faults neither create nor destroy lithosphere, is a type of fault whose relative motion is predominantly horizontal in either sinistral or dextral direction. Furthermore, transform faults end abruptly...
and convergent type plate boundaries
Convergent boundary
In plate tectonics, a convergent boundary, also known as a destructive plate boundary , is an actively deforming region where two tectonic plates or fragments of lithosphere move toward one another and collide...
in a complex zone at the northern end of South Island. The presumed epicenter of the 1843 earthquake is not, however, associated with any known fault.
Earthquake characteristics
Very little is known about the details of this earthquake except that it lasted for a few minutes. There is insufficient information to identify the epicenter or say anything about the type or amount of displacement involved.Damage
Damage in the Wanganui area reached IX-X on the Mercalli intensity scaleMercalli intensity scale
The Mercalli intensity scale is a seismic scale used for measuring the intensity of an earthquake. It measures the effects of an earthquake, and is distinct from the moment magnitude M_w usually reported for an earthquake , which is a measure of the energy released...
. Many houses were damaged, and a brick church at Pūtiki was destroyed. There was extensive lateral spreading of the terrace margin to the Whanganui River
Whanganui River
The Whanganui River is a major river in the North Island of New Zealand.Known for many years as the Wanganui River, the river's name reverted to Whanganui in 1991, according with the wishes of local iwi. Part of the reason was also to avoid confusion with the Wanganui River in the South Island...
, 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.