North Island Fault System
Encyclopedia
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 (right lateral) strike-slip component of the oblique convergence of the Pacific Plate
with the Australian Plate. They include the Wairarapa Fault
and Wellington Fault
to the southwest, the Ruahine and Mohaka Faults in the central section and the Waimana, Waiotahi, Whakatane and Waiohau Faults to the northeast. Most of the fault system consists of dextral strike-slip faults, although towards its northeastern end the trend swings to more S-N trend and the faults become mainly oblique normal in sense as the zone intersects with the Taupo rift zone. This fault zone accommodates up to 10 mm/yr of strike-slip displacement.
on the southern coast of North Island up to near Woodville
, where the fault branches into the Mohaka and Ruahine Faults. No historical earthquakes have been recorded along this fault although a significant event is estimated to have occurred within the last 1,000 years. The recurrence interval for large earthquakes on this fault is estimated to be less than 2,000 years. Three main segments have been identified, the Wellington-Hutt section, the Tararua section and the Pahiatua section.
, running along the lake's northwestern edge. The 1855 Wairarapa earthquake
was caused by movement along this fault. The recurrence interval for large earthquakes on this fault is less than 2,000 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 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...
that carry most of the dextral (right lateral) strike-slip component of the oblique convergence of the 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....
with the Australian Plate. They include the Wairarapa Fault
Wairarapa Fault
The Wairarapa Fault is an active seismic fault in the southern part of the North Island of New Zealand. It is a dextral strike-slip fault with a component of uplift to the northwest as expressed by the Rimutaka Range...
and Wellington Fault
Wellington Fault
The Wellington Fault is an active seismic fault in the southern part of the North Island of New Zealand. It is a dextral strike-slip fault with variable amounts of vertical movement causing uplift to the northwest, as expressed by a series of ranges...
to the southwest, the Ruahine and Mohaka Faults in the central section and the Waimana, Waiotahi, Whakatane and Waiohau Faults to the northeast. Most of the fault system consists of dextral strike-slip faults, although towards its northeastern end the trend swings to more S-N trend and the faults become mainly oblique normal in sense as the zone intersects with the Taupo rift zone. This fault zone accommodates up to 10 mm/yr of strike-slip displacement.
Faults
The North Island Fault System consists of eight main fault strands and many other smaller related faults.Wellington Fault
The Wellington Fault is a dextral strike-slip fault that runs from the Cook StraitCook Strait
Cook Strait is the strait between the North and South Islands of New Zealand. It connects the Tasman Sea on the west with the South Pacific Ocean on the east....
on the southern coast of North Island up to near Woodville
Woodville, 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...
, where the fault branches into the Mohaka and Ruahine Faults. No historical earthquakes have been recorded along this fault although a significant event is estimated to have occurred within the last 1,000 years. The recurrence interval for large earthquakes on this fault is estimated to be less than 2,000 years. Three main segments have been identified, the Wellington-Hutt section, the Tararua section and the Pahiatua section.
Wairarapa Fault
The Wairarapa Fault extends from near the coast just southwest of Lake WairarapaLake Wairarapa
Lake Wairarapa is a lake at the southern end of the North Island of New Zealand, 50 kilometers east of Wellington. The lake covers an area of 78 km², and is the third largest in the North Island, fractionally smaller than Lake Rotorua...
, running along the lake's northwestern edge. The 1855 Wairarapa earthquake
1855 Wairarapa earthquake
The 1855 Wairarapa earthquake occurred on 23 January at about 9 p.m. In Wellington, close to the epicenter, shaking lasted for at least 50 seconds. The magnitude of the earthquake is estimated to have been in the range 8.1-8.3, the most powerful recorded in New Zealand since systematic European...
was caused by movement along this fault. The recurrence interval for large earthquakes on this fault is less than 2,000 years.