Alpine Fault

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For the Auckland band of this name, see Alpine Fault (band).

The Alpine Fault is clearly visible from space, running along the western edge of the Southern Alps from the southwestern coast towards the northeastern corner of the South Island.

Tectonic map of the New Zealand plate boundary which controls the Alpine Fault, USGS

This map, coloured by elevation, shows how the Alpine Fault affects the topography of the South Island's West Coast. The region shown is 495 km (307 mi) long; northwest is at the top.

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 southwestern 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.

1 Historic earthquakes
2 Major ruptures
3 See also
4 References
5 External links

[edit] Historic earthquakes

The Alpine Fault and its northern offshoots have experienced sizeable earthquakes in historic times:

1848 - Marlborough. Estimated magnitude = 7.5.
1888 - North Canterbury. Estimated magnitude = 7.3.
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.

[edit] 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 say that a similar earthquake could happen at any time as the interval since 1717 is longer than between the earlier events.[1]

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

[edit] See also

[edit] References

Robinson, R. (2003). Potential earthquake triggering in a complex fault network: the northern South Island, New Zealand. Geophysical Journal International, 159(2), 734-748. (abstract)
Wells, A., Yetton, M.T., Duncan, R.P., and Stewart, G.H. (1999) Prehistoric dates of the most recent Alpine fault earthquakes, New Zealand. Geology, 27(11), 995-998. (abstract)