The Awatere Fault is an active dextral (right lateral)

strike-slip fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

in the northeastern part of

South Island The South Island, also officially named , is the larger of the two major islands of New Zealand in surface area, the other being the smaller but more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman ...

, 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 Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and Iza ...

, from the transform Alpine Fault to the

Hikurangi Trench The Hikurangi Trench, also called the Hikurangi Trough, is an oceanic trench in the bed of 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. It is the ...

subduction zone Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

. The

1848 Marlborough earthquake The 1848 Marlborough earthquake was a 7.5 () earthquake that occurred at 1:40 a.m. on 16 October 1848 and whose epicentre was in the Marlborough region of the South Island of New Zealand. In Wellington, the shaking lasted for about two min ...

was caused by rupture of the whole of the eastern section of the Awatere Fault.

Extent

The 175 km long Awatere Fault is formed of two main segments; the Molesworth section to the southwest and the Eastern section to the northeast. A further strand links the southwestern end of the Eastern section to the Clarence Fault, passing through Barefell Pass.

Molesworth section

The Molesworth segment of the Awatere Fault runs from close to the junction between the Alpine and Wairau Faults near Lake Tennyson, to near

Molesworth Station Molesworth Station is a high country cattle station. It is located behind the Inland Kaikoura Mountain range in the South Island's Marlborough District. It is New Zealand's largest farm, at over and supports the country's biggest herd of ...

in the northeast. It is about 55 km in length and consists of several smaller segments. This section has an overall strike of N75–80°E, giving local zones of transtension at some of the segment boundaries, such as at Isolated Flat.

Eastern section

The Eastern section of the fault runs from Molesworth Station to the coast, near White Bluffs, without significant segmentation. The Awatere River follows the trace of much of the eastern section of the fault, giving its name to the whole structure.

Recent seismicity

The Molesworth section appear to have moved twice since about 3000 years ago, in events with slip values of about 6–7 m. Trenching at Saxton River at the eastern end of the Molesworth section suggests 8 ruptures since about 6,300 years ago, with an estimated mean recurrence of about 800 years. Evidence from the eastern section of the fault suggests that there were 9–10 earthquakes in the period from 8610 BP to AD 1848. This gives a mean recurrence interval of 820–950 years. In 1848 a minimum 105 km length section of the fault ruptured, causing an earthquake of an estimated magnitude of about 7.5 . The rupture appears to have bypassed the Molesworth section of the fault, continuing on the southern strand through Barefell Pass.

Seismic hazard

Seismic hazard on the Eastern section is considered low, with only about 150 years since the last major earthquake on that section and an estimated recurrence interval of 600–2500 years.

References

{{Seismic faults of New Zealand Seismic faults of New Zealand Strike-slip faults