Alpine Fault

The Alpine Fault is a geological fault, specifically 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. 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.