California Drive, Totara Park, Upper Hutt

The Wellington Fault is an active seismic fault in the southern part of the

North Island The North Island, also officially named Te Ika-a-Māui, is one of the two main islands of New Zealand, separated from the larger but much less populous South Island by the Cook Strait. The island's area is , making it the world's 14th-largest ...

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

. It is a 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 ...

with variable amounts of vertical movement causing uplift to the northwest, as expressed by a series of ranges. It forms part of the

North Island Fault System The North Island Fault System (also known as North Island Dextral Fault Belt or NIFS) is a set of southwest–northeast trending seismically-active faults in the North Island of New Zealand that carry most of the dextral (right lateral) strike- ...

, which accommodates the transfer of displacement along the oblique convergent boundary between the

Indo-Australian Plate The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and the surrounding ocean and extends northwest to include the Indian subcontinent and the adjacent waters. It was formed by the fusion of the Indian an ...

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 ...

Geometry

The Wellington Fault consists of three main sections.

Wellington-Hutt Valley section

This 75 km long curved fault segment is mapped on the floor of the Cook Strait before crossing the Wellington peninsula through Long Gully and along the northwestern edge of Wellington Harbour, past Lower Hutt terminating near

Kaitoke Kaitoke (sometimes called Pakuratahi), part of Upper Hutt City, is a locality in the southern North Island of New Zealand. It is located at the northern end of the Hutt Valley, 45 kilometres northeast of Wellington City and six kilometres from the ...

. This segment has had a lateral slip-rate of 6.0–7.6 mm per year for at least the last 140,000 years, from the progressive offset of

dated Date or dates may refer to: *Date (fruit), the fruit of the date palm (''Phoenix dactylifera'') Social activity *Dating, a form of courtship involving social activity, with the aim of assessing a potential partner **Group dating *Play date, an ...

river terrace Fluvial terraces are elongated terraces that flank the sides of floodplains and fluvial valleys all over the world. They consist of a relatively level strip of land, called a "tread", separated from either an adjacent floodplain, other fluvial te ...

s. The most recent rupture event along this section is constrained to 150–450 yrs BP. This section is interpreted to give rise to

characteristic earthquake Earthquake prediction is a branch of the science of seismology concerned with the specification of the time, location, and magnitude of future earthquakes within stated limits, and particularly "the determination of parameters for the ''next'' s ...

s involving rupture of the entire fault segment, with a single-event displacement of 3.8–4.6 m. The recurrence interval is 500–770 years. The Kaitoke basin is a small

pull-apart basin In geology, a basin is a region where subsidence generates accommodation space for the deposition of sediments. A pull-apart basin is a structural basin where two overlapping (en echelon) strike-slip faults or a fault bend creates an area of cru ...

formed at the 2 km lateral offset between this segment and the Tararua segment, near Kaitoke. It is possible that the Māori legend of the formation of Whanganui-a-Tara (Wellington Harbour) derives from an oral record of an early quake along this fault.

Tararua section

The 53 km long arcuate Tararua segment starts just north of Kaitoke along the eastern side of the

Tararua Range The Tararua Range, often referred to as the Tararua Ranges or Tararua, is one of several mountain ranges in the North Island of New Zealand. The Tararua Range runs northeast–southwest for from near Palmerston North to the upper reaches of ...

. It terminates near Putara. It consists of two active fault strands, the southeasterly of which carries most of the displacement, as shown by offset drainage patterns. The strike of this section changes from 041° in the south to 020° in the north. The dextral slip rate for this section is 4.9–7.6 mm/yr, with a single-event displacement of 3.5–5.5 m and a recurrence interval of 500–1120 years.

Pahiatua section

This 42 km long segment runs from near Putara in the south to near Woodville in the north, where the fault branches into the Ruahine and Mohaka Faults. This segment is relatively linear with a strike of 033°. The dextral slip rate for this section is 4.9–6.2 mm/yr, with a single-event displacement of 4.5±1 m and a recurrence interval of 560–1120 years.

Seismic hazard

Although no historic earthquake has been recorded for this fault, the potential impact of rupture along the Wellington-Hutt Valley section on the Wellington area makes it one of the greatest natural hazards in New Zealand. The Wellington Fault is also capable of producing earthquakes of up to magnitude-8. While a major rupture on the Wellington Fault can be expected anytime in the next 500 years, a significant earthquake on other faults in the Wellington area have a shorter 150 year return time.

Notes

References

*Richard W. Heine: ''A New Interpretation of the Geomorphology of Wellington''. In ''Journal of the Royal Society of New Zealand'', Juni 1982, p. 189–205 ()

External links

Wellington Fault
at GNS Science
''Wellington Fault''
– video by GNS Science (10 min.) * {{Seismic faults of New Zealand Seismic faults of New Zealand Wellington Region Hawke's Bay Region Strike-slip faults