Wellington Fault
Encyclopedia
The Wellington Fault is an active seismic fault
in the southern part of the North Island
of New Zealand
. It is a dextral (right-lateral) strike-slip fault 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
, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate
and Pacific Plate
.
. 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
river terraces. The most recent rupture event along this section is constrained to 150–450 yrs BP
. This section is interpreted to give rise to characteristic earthquakes 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
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.
. 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.
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.
Active fault
An active fault is a fault that is likely to have another earthquake sometime in the future. Faults are commonly considered to be active if there has been movement observed or evidence of seismic activity during the last 10,000 years....
in the southern part of the North Island
North Island
The North Island is one of the two main islands of New Zealand, separated from the much less populous South Island by Cook Strait. The island is in area, making it the world's 14th-largest island...
of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. It is a dextral (right-lateral) strike-slip fault 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
North Island Fault System
The North Island Fault System or North Island Dextral Fault Belt is a set of southwest-northeast trending seismically-active faults in the North Island of New Zealand that carry most of the dextral strike-slip component of the oblique convergence of the Pacific Plate with the Australian Plate...
, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate
Indo-Australian Plate
The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and surrounding ocean, and extends northwest to include the Indian subcontinent and adjacent waters...
and Pacific Plate
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic plate....
.
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 Valley and along the northwestern edge of Wellington Harbour, past Lower Hutt terminating near KaitokeKaitoke
Kaitoke, 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 northern end of the Upper Hutt urban area...
. 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
Radiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
river terraces. The most recent rupture event along this section is constrained to 150–450 yrs BP
Before Present
Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...
. This section is interpreted to give rise to characteristic earthquakes 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
Pull Apart Basin
250px|thumb|[[Cami Lake]] in [[Tierra del Fuego]] develops on a [[Patagonian Ice Sheet|glacially]] excavated pull apart basin along the [[Magallanes-Fagnano Fault]], hence its elongated form...
formed at the 2 km lateral offset between this segment and the Tararua segment, near Kaitoke.
It is possible that the Māori legend
Maori mythology
Māori mythology and Māori traditions are the two major categories into which the legends of the Māori of New Zealand may usefully be divided...
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 RangeTararua Range
The Tararua Range is one of several mountain ranges in the North Island of New Zealand which form a ridge running parallel with the east coast of the island between East Cape and Wellington....
. 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 WoodvilleWoodville, New Zealand
Woodville is a small town in the southern North Island of New Zealand, 75 km north of Masterton and 25 km east of Palmerston North. In the 2006 census 1,398 people are usually resident in Woodville, a decrease of 81 people, or 5.5%, since the 2001 Census.-Early History and Local...
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.External links
- Wellington Fault – video by GNS Science (10 min.)