The Alpine Fault is a geological fault, 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 associated earth movements, have formed the Southern Alps.

Beginning off the south-western corner of the South Island, the Alpine Fault runs along the western edge of the Southern Alps, then splits into three parallel faults north of Arthur's Pass. Average slip rates in the fault's central region are about 30mm a year, very fast by global standards.

Contents

1 Historic Earthquakes 2 Major Ruptures 3 See also 4 External links

Historic Earthquakes

The Alpine Fault has experienced sizeable earthquakes in historic times:

• 1929 - Arthur's Pass. Estimated magnitude = 7.1.
• 1929 - Murchison. Estimated magnitude = 7.8.
• 1968 - Inangahua. Estimated magnitude = 7.1.
• 2003 - Fiordland. Estimated magnitude = 7.1.

Major Ruptures

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 400km of the southern two thirds of the fault. Scientists' best estimate is that there is a high likelihood of a similar earthquake within a few decades.

Large ruptures can also trigger earthquakes on the faults continuing north from the Alpine Fault.

See also

• Earthquake
• Plate Tectonics
• Seismology

External links

University of Otago Geology Department:

• Overview http://www.otago.ac.nz/geology/af/alpinefault.htm
• Virtual Field Trip http://www.otago.ac.nz/geology/features/aftrip/start.htm
• Potential effects of major rupture http://www.otago.ac.nz/geology/features/earthquake/fj400af.htm

Institute of Geological & Nuclear Sciences Limited (GNS):

• Map of New Zealand's Historic Earthquakes http://www.gns.cri.nz/what/earthact/earthquakes/historic.html
• FAQ on Alpine Fault http://www.gns.cri.nz/what/earthact/earthquakes/earthquakefaq.html#21
• Press release, 10 September 1998 http://www.gns.cri.nz/news/release/alpf.html

Miscellaneous:

• Abstract http://www.blackwellpublishing.com/abstract.asp?aid=25&iid=2&ref=0956-540X&vid=1
  59 of Robinson (2003), Potential earthquake triggering in a complex fault network: the northern South Island, New Zealand, Geophysical Journal International, 159(2), 734-748]
• Earthquakes and Tectonics in New Zealand http://www.natureandco.co.nz/land_and_wildlife/landforms/tectonics/idx_tect.php3