Alpine Fault
Encyclopedia
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
. Earthquake
s along the fault, and the associated earth movements, have formed the Southern Alps
. The uplift to the southeast of the fault is due to an element of convergence between the plates, meaning that the fault has a significant high-angle reverse oblique component to its displacement.
The Alpine Fault is believed to align with the Macquarie Fault Zone
in the Puysegur Trench
off the southwestern corner of the South Island. From there, the Alpine Fault runs along the western edge of the Southern Alps, before splitting into a set of smaller dextral strike-slip faults north of Arthur's Pass, known as the Marlborough Fault System
. This set of faults, which includes the Wairau Fault
, the Hope Fault
, the Awatere Fault
, and the Clarence Fault
, transfer displacement between the Alpine Fault and the Hikurangi subduction zone
to the north. The Hope fault is thought to represent the primary continuation of the Alpine fault.
Average slip rates in the fault's central region are about 30mm a year, very fast by global standards.
Over the last thousand years, there have been four major ruptures along the Alpine Fault causing earthquakes of about magnitude 8. These occurred in approximately 1100, 1450, 1620 and 1717 AD, at intervals between 100 and 350 years. The 1717 quake appears to have involved a rupture along nearly 400 km of the southern two thirds of the fault. Scientists say that a similar earthquake could happen at any time as the interval since 1717 is longer than between the earlier events.
Large ruptures can also trigger earthquakes on the faults continuing north from the Alpine Fault. There is paleotsunami evidence of near-simultaneous ruptures of the Alpine fault and Wellington (and/or other major) faults to the North having occurred at least twice in the past 1,000 years.
University of Otago Geology Department:
Institute of Geological & Nuclear Sciences Limited (GNS Science
):
Miscellaneous:
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...
's 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...
. It forms a transform boundary between the 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....
and the Indo-Australian Plate
Indo-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...
. 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...
s along the fault, and the associated earth movements, have formed the Southern Alps
Southern Alps
The Southern Alps is a mountain range extending along much of the length of New Zealand's South Island, reaching its greatest elevations near the island's western side...
. The uplift to the southeast of the fault is due to an element of convergence between the plates, meaning that the fault has a significant high-angle reverse oblique component to its displacement.
The Alpine Fault is believed to align with the Macquarie Fault Zone
Macquarie Fault Zone
The Macquarie Fault Zone is a major right lateral-moving transform fault along the seafloor of the south Pacific Ocean which runs from New Zealand southwestward to the Macquarie Triple Junction...
in the Puysegur Trench
Puysegur trench
The deep Puysegur Trench is a deep cleft in the floor of the south Tasman Sea formed by the subduction of the Indo-Australian Plate under the Pacific Plate to the south of New Zealand. Immediately to its east lies a ridge, a northern extension of the Macquarie Ridge, which separates the Puysegur...
off the southwestern corner of the South Island. From there, the Alpine Fault runs along the western edge of the Southern Alps, before splitting into a set of smaller dextral strike-slip faults north of Arthur's Pass, 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...
. This set of faults, which includes the Wairau Fault
Wairau Fault
The Wairau Fault is an active dextral strike-slip fault in the northeastern part of South Island, New Zealand. It forms part of the Marlborough Fault System, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate and Pacific Plate,...
, the Hope Fault
Hope Fault
The Hope Fault is an active dextral strike-slip fault in the northeastern part of South Island, New Zealand. It forms part of the Marlborough Fault System, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate and Pacific Plate,...
, the Awatere Fault
Awatere Fault
The Awatere Fault is an active dextral strike-slip fault in the northeastern part of South Island, New Zealand. It forms part of the Marlborough Fault System, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate and Pacific Plate,...
, and the Clarence Fault
Clarence Fault
The Clarence Fault is an active dextral strike-slip fault in the northeastern part of South Island, New Zealand. It forms part of the Marlborough Fault System, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate and Pacific Plate,...
, transfer displacement between the Alpine Fault and the Hikurangi subduction zone
Hikurangi Trench
The Hikurangi Trench is a linear deep in the Pacific Ocean off the east coast of the North Island of New Zealand, lying between the southern end of the Cook Strait and the Chatham Rise. Though much shallower, it is the southward continuation of the Kermadec Trench and forms part of the...
to the north. The Hope fault is thought to represent the primary continuation of the Alpine fault.
Average slip rates in the fault's central region are about 30mm a year, very fast by global standards.
Historic earthquakes
The Alpine Fault and its northern offshoots have experienced sizeable earthquakes in historic times:- 1848 - Marlborough1848 Marlborough earthquakeThe 1848 Marlborough earthquake is the name associated with a severe earthquake which occurred at 1:40 a.m. on 16 October 1848 and whose epicenter was in the Marlborough region of the South Island of New Zealand....
, estimated magnitude = 7.5 - 1888 - North Canterbury1888 North Canterbury earthquakeThe 1888 North Canterbury earthquake is the name associated with a severe earthquake which occurred at 4.10 a.m on 1 September 1888 following a sequence of foreshocks that started the previous evening, and whose epicentre was in the North Canterbury region of the South Island of New Zealand.In...
, estimated magnitude = 7.3 - 1929 - Arthur's Pass1929 Arthur's Pass earthquakeThe 1929 Arthur's Pass Earthquake occurred at 10.50pm NZMT on 9 March 1929 . The sparsely settled region of the Southern Alps shook for four minutes...
, estimated magnitude = 7.1 - 1929 - Murchison1929 Murchison earthquakeThe 1929 Murchison earthquake occurred at 10:17 AM on 17 June. It struck the Murchison region of South Island, with an estimated magnitude of 7.8, and was felt throughout New Zealand. There were 17 casualties, mostly as a result of landslides triggered by the earthquake...
, estimated magnitude = 7.8 - 1968 - Inangahua, estimated magnitude = 7.1
- 2003 - FiordlandFiordlandFiordland is a geographic region of New Zealand that is situated on the south-western corner of the South Island, comprising the western-most third of Southland. Most of Fiordland is dominated by the steep sides of the snow-capped Southern Alps, deep lakes and its ocean-flooded, steep western valleys...
, estimated magnitude = 7.1 - 2009 - Fiordland2009 Fiordland earthquakeThe 2009 Fiordland earthquake was a magnitude 7.8 earthquake that struck the South Island of New Zealand at 9:22 pm on 15 July 2009. The earthquake was centred in the remote region of Fiordland, with the epicentre located west-north-west of Invercargill near Dusky Sound in Fiordland National...
, estimated magnitude = 7.8
Major ruptures
Large ruptures can also trigger earthquakes on the faults continuing north from the Alpine Fault. There is paleotsunami evidence of near-simultaneous ruptures of the Alpine fault and Wellington (and/or other major) faults to the North having occurred at least twice in the past 1,000 years.
External links
Otago Regional CouncilUniversity of Otago Geology Department:
Institute of Geological & Nuclear Sciences Limited (GNS Science
GNS Science
GNS Science is a New Zealand Crown Research Institute. It focuses on geology, geophysics , and nuclear science ....
):
- Interactive map New Zealand Active Faults Database.
- Map of New Zealand's Largest Earthquakes
- FAQ on Alpine Fault
- Press release, 10 September 1998
Miscellaneous: