Taranaki Blowout earthquake locations

Information and graphic courtesy of GNS Science
The Taranaki Fault is a crustal scale thrust of at least 600 km in length that lies at the eastern margin of the Taranaki Basin . The fault forms the pre-Miocene edge of the basin.

Younger sediments form an unbroken cover over the fault so that it is not exposed at the surface. The Taranaki Fault is part of a larger fault system, including the Waimea-Flaxmore and Manaia faults and the Tarata Thrust, which extends from the Alpine Fault in the South Island up through western North Island .

Early petroleum exploration using gravity data indicated that the eastern margin of the Taranaki Basin was bounded by a large fault, although it was not until the acquisition of seisimc reflection data in the 1970s that the immense size and nature of the fault was recognised. Commercial oil reserves have been found in structures associated with the fault mainly under the Taranaki Peninsula.

Interpretation of seismic-reflection data indicates that the dip of the principal fault surface ranges from 25 to 45° and increases southwards. The principal fault is corrugated on length scales of 10's to 100's of kilometres, and is accompanied by multiple slip surfaces which often splay from the main fault within 2-5 km of the upper tip. Splays can be entirely within Tertiary or basement rocks, or may produce inter-fingering of basement and Cretaceous-Tertiary strata. These splays are discontinuous and extend for no more than 10-50 km along strike.