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45-627: The North Island Fault System ( NIFS ) (also known as North Island Dextral Fault Belt or North Island Shear Belt ) is a set of southwest–northeast trending seismically-active faults in the North Island of New Zealand that carry much of the dextral (right lateral) strike-slip component of the oblique convergence of the Pacific Plate with the Australian Plate . However despite at least 3 km (1.9 mi) of uplift of

90-466: A bit of grade III. There are several Department of Conservation (DOC) campsites, hot pools and plenty of undisturbed native bush. After approximately 36 km, it comes out of the Kawekas and farmland becomes more common The river bends itself into an oxbow and shortly after rapids become larger as it leads into the grade III section. DOC campsites are still found along this 68 km stretch. As

135-799: A brief while the Te Whaiti Fault is the most western active fault of the system before it merges with a splay of the Waiohau Fault which terminates at the head of the Rangitaiki River valley. The Waimana Fault is to the east of the Whakatane Fault both of which join the Mohaka Fault in the south of the system To its north it has an off shore portion that terminates against the White Island Fault which

180-615: A sedimentary rock canyon. The boulders, while impressive in size, are even more intriguing because of the holes and depressions the water has carved into them. House rock worth a closer look; the center has been carved out and is accessible only by a hole in the side. Fossilized shells and organic matter have been remarkably well preserved in the stones. After the Willow Flat Bridge, the size and frequency of large boulders decreases to be replaced by steep vegetation covered terraces. Sandstone and mudstone become more prevalent as

225-728: A shallow megathrust earthquake. In the southern portion of the system around Wellington the subduction slab deep earthquakes of the Wadati–Benioff zone are off shore to the west. The Kermadec microplate , which is presently in terms of movement, an independent part of the Australian Plate, probably extends to Cook Strait , with the Kermadec Plate's unclear south western boundary being the North Island Fault System. The western boundary of this plate

270-474: A shuttle. The upper section is the most popular destination for fishing in Hawke's Bay. Trout is a common catch, along with various varieties of native fish. Mainly brown trout are found above Pakaututu bridge and rainbow trout below. Fishing is not as good on the lower sections but the rapids are more exciting and challenging. Hiking is popular along the upper section. Trails lead to the hot springs and access

315-647: 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. The Whakatane Fault is where the North Island Fault System intersects the Taupo Rift and so displacement across

360-732: Is considered to be a geologic hazard – one related to earthquakes as a cause. Effects of movement on an active fault include strong ground motion , surface faulting, tectonic deformation , landslides and rockfalls , liquefaction , tsunamis , and seiches . Quaternary faults are those active faults that have been recognized at the surface and which have evidence of movement during the Quaternary Period. Related geological disciplines for active-fault studies include geomorphology , seismology , reflection seismology , plate tectonics , geodetics and remote sensing , risk analysis , and others. Active faults tend to occur in

405-512: Is currently associated with to its north the spreading center of the back arc Lau Basin which continues to the south as the Havre Trough and this becomes the Taupō Rift which is the western boundary of the northern North Island Fault System and hosts the active Taupō Volcanic Zone . The two islands of New Zealand are separated by Cook Strait but the fault system effectively merges to

450-563: Is employed with other factors to determine the potential earthquake hazard. The geologic conditions and plate tectonic setting in much of the Western U.S. has resulted in the region being underlain by relatively thin crust and having high heat flow, both of which can favor relatively high deformation rates and active faulting. In contrast, in the Central and Eastern U.S. (CEUS) the crust is thicker, colder, older, and more stable. Furthermore,

495-711: Is less than 2,000 years. There are associated faults such as the Wharekauhau Thrust to the south and the Mangaoranga Fault to the north that might partake in a propagating rupture. The Wellington Fault is a dextral strike-slip fault that runs from the Cook Strait 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

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540-543: Is obliquely converging at over 4 cm/year (1.6 in/year) with the oceanic Pacific Plate at the Hikurangi Margin , and the North Island Fault System carries most of the dextral (right lateral) strike-slip component of this convergence. The amount assigned to the strike slip component varies down the fault system as for example offshore of Gisborne , which is near the north east of the system, approximately 6 cm/year (2.4 in/year) of plate subduction

585-527: Is occurring while off the Wairarapa shore this decreases to perhaps 2 cm/year (0.79 in/year). The Hikurangi Plateau , a remnant of a large igneous province is being subducted under the North Island at this margin currently, and these subducted parts are reaching 37–140 km (23–87 mi) into the mantle beneath the North Island and northern South Island. So in the northern two thirds of

630-575: Is on the North Island of New Zealand in the east central region of Hawke’s Bay . Mohaka is a Maori word, roughly translated it means “place for dancing”. The iwi (Māori tribes) associated with the Mohaka River are Ngāti Pāhauwera , Ngāti Hineuru , Ngāti Tūwharetoa and Mana Ahuriri. The headwaters are found in the Kaweka and Kaimanawa ranges. From the range it winds southeast before twisting northeast and finally southeast again to empty into

675-611: Is the eastern margin of the Taupō Rift . The Waiohau Fault extends from the end of the Ruahine Fault north towards the Bay of Plenty for 61 km (38 mi). The slip rate is 0.14 cm/year (0.055 in/year) with estimated movement of a multisegment fault rupture of M w  7.1 with an average recurrence of 3000 years. It lies roughly parallel with, and to the west of, the Whakatane, Waimana, and Waiotahi Faults, and to

720-560: The Pacific Ocean near the town of Mohaka. There are many gorges on the Mohaka; some as steep as 200m (656 feet). Its main tributaries are the Waipunga, Taharua, Hautapu rivers. The full length is 172 kilometres (107 mi) and it drains a basin of 2,357 square kilometres (910 sq mi). The Mohaka Viaduct is a railway bridge over the lower Mohaka river. The Napier–Taupo road ( State Highway 5 ) has had several bridges over

765-764: The Waiohau Fault which has several geologically active splays. There is a western splay of the Ruahine Fault before this to the Kaweka Fault around the Mohaka River valley. The Kaweka Fault remains the most western fault until it becomes in turn the Wheao Fault in the Waipunga River valley. The Te Whaiti Fault is a splay towards the NNE of the Wheao Fault that rejoins it near Murupara and for

810-525: The Whakatane Fault which has an off shore extension. The Whakatane Fault has multisegment capacity for a size M w  7 earthquake at a recurrence interval of 3000 years and slip rate of 0.1 cm/year (0.039 in/year). To the east of the Mohaka Fault is the Patoka Fault which commences in the Tutaekuri River valley within 500 m (1,600 ft) of a Mohaka Fault splay. Where

855-549: The CEUS is thousands of miles from active plate boundaries, so the rates of deformation are low in this region. Nevertheless, the CEUS has had some rather large earthquakes in historical times, including a series of major earthquakes near New Madrid, Missouri in 1811–1812 , a large earthquake near Charleston, South Carolina in 1886, and the Cape Ann earthquake northeast of Boston in 1755. Mohaka River The Mohaka river

900-399: The Mohaka Fault, it appears that the Ruahine Fault has displacement rates of just above 0.5 cm/year (0.20 in/year) and had a transition from episodic dip-slip-dominated displacement during the late Miocene–Pliocene to oblique-slip and strike-slip-dominated offset more recently. The Ruahine Fault commenced its vertical displacement about 10 million years ago in the late Miocene. Most of

945-422: The Mohaka to transport timber. In 2004 a water conservation order was placed on the upper section of the Mohaka because of its fantastic fishing, scenic gorges and outstanding amenity for recreation. The area is also an important habitat for the rare blue duck . More recently it is a popular spot for rafting, kayaking, tramping and fishing. Up in the Kaweka range the Mohaka is a twisting grade II river with

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990-462: The Mohaka. Most sections can be run as a day trip or sections can be combined into multi day adventures. The Mohaka offers something for any level of kayaking . Beginners will find plenty of eddies and waves on the grade II sections while intermediate kayakers will find the grade III more challenging. The grade V is a technical run for more advanced kayakers. Local rafting companies have the most up-to-date information and can often assist in setting up

1035-829: The Potaka Fault intercepts the Esk Forest its most eastern active splay becomes the Rukumoana Fault . The Potaka Fault terminates just south of the peak Tauwhare Papauma on State Highway 5 . The Rukumoana Fault has an active northern splay called the Rangiora Fault and both terminate in the region of Hawke's Bay north of Lake Tutira . Where the Rangiora Fault terminates the Waiotahi Fault to its north by about 20 km (12 mi) becomes

1080-414: The Ruahine Fault presently accommodates down to the east vertical displacements but between 4 and 3 million years ago 200 m (660 ft) up to the east vertical displacement has been found on a portion of the fault. In the last 3.6 million years geological studies have shown that less than 10 km (6.2 mi) of dextral offset has occurred on the Ruahine Fault. At its northern end this fault becomes

1125-544: The Wakarara Range. The Mohaka Fault has had about 300 m (980 ft) of strike-slip displacement in the last 2 million years. As the Wellington Fault branches near Woodville, the more northwesterly branch is known as the Ruahine Fault. Results from trenching over this fault suggest an earthquake recurrence interval of 400–500 years, with typical offsets in the range 3.0–5.5 m. Similarly to

1170-541: The Wellington Fault is known as the Mohaka fault. The fault splays to the north, onto the Waimana Fault , which itself has branches of the Waiotahi and Waioeka Faults . The Waimana Fault is 50 km (31 mi) long with potential for a M w 6.9 shock at its recurrence interval of 2850 years and slip rate of 0.07 cm/year (0.028 in/year). The main segment of the Mohaka Fault eventually passes into

1215-496: The Whakatane Fault is expected to be oblique, with both normal dip-slip (1.5 ± 0.5 mm/year) and right-lateral strike-slip (1.1 ± 0.5 mm/year) components of motion. The known three surface-rupturing prehistoric earthquakes over the last 10,000 years were associated with net slip at the ground surface of about 3 m (9.8 ft). In this south eastern portion of the North Island, the continental Australian Plate

1260-462: The White Island Fault of the Taupō Rift. The Karanga Fault terminates in the mountains 20 km (12 mi) south of Opotiki. The Wairarapa Fault extends from near the coast just southwest of Lake Wairarapa , running along the lake's northwestern edge. The M w  8.2 1855 Wairarapa earthquake was caused by movement along this fault. The recurrence interval for large earthquakes on this fault

1305-577: The axial ranges in the middle regions of the fault system during the last 10 million years most of the shortening on this part of the Hikurangi Margin is accommodated by subduction. The faults 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

1350-413: The banks get steeper and the rapids start off with the largest one on the river, Long Rapid. Scenery on this stretch includes massive boulders, waterfalls falling from the steep canyon walls and fascinating erosion patterns created by the water on the soft stones. The rapids are continuous for the full 18 km with the grade being mostly III+ with some exciting IV/V. The final stretch of the river after

1395-484: The east of the Taupo Rift . At its southern end it is a dextral strike-slip fault, becoming a normal dip-slip fault for the northern part of its length. The valley of the Rangitaiki River approximately follows the line of the fault. It terminates against the eastern margin of the Taupō Rift in the on shore portion of the Whakatāne Graben . The fault is believed to be responsible for an earthquake in 1866 which

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1440-495: 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 Taupō Rift . This fault zone accommodates up to 1 cm/year (0.39 in/year) of strike-slip displacement. The North Island Fault System consists of eight main fault strands and many smaller related faults that are also currently active. The more southeasterly branch of

1485-436: The fault system, as well as the shallow earthquakes of the system, there are also deeper earthquakes associated with the subduction slab. Modelling since the well characterised but atypically large displacements of the 2016 Kaikōura earthquake suggests the possibility that the large displacements seen in the last great earthquake in the system, that of 1855, compared to classic earthquake fault modelling, may have been related to

1530-419: The grade V returns to grade II as it mellows and flows into the ocean. More steep walled banks of river and side creeks can be seen down this section as they cascade down, creating substantially high tiered waterfalls and smaller side gorges. The vegetation changes to become more lush, featuring silver fern or punga, eventually easing off to cleared farm land towards the ocean Water level is usually highest in

1575-434: The last 2.3 million years the maximum vertical displacement has been at least a further 500 m (1,600 ft) found about 30 km (19 mi) south of Hawkston. It is noted that at Hawkston itself there has been no vertical displacement although both the southern end and northern end of the fault there has been vertical displacement during this period. The souther displacement of about 350 m (1,150 ft) produced

1620-497: The more technical grade III rapids begin the river flows past native bush of the Tataraakina block on the left and Waitere Station on the right. This section contains Te Hoe's rapid, which is the largest and longest in this section. There are 3 gorges to be appreciated on this run. Te Kooti’ s bridge marks the start of the grade V and the end of the grade III. After the bridge, it is an easy grade II float for about 4 km then

1665-400: The most eastern active fault in the system. There has been a transition from episodic dip-slip-dominated displacement during the late Miocene–Pliocene to oblique-slip and strike-slip-dominated offset more recently. Prior to the late Miocene, before about 11 million years ago, at least 500 m (1,600 ft) of western vertical displacement occurred on the Mohaka Fault, and more recently, in

1710-399: The river approaches the ocean, as does farmland. Approximately seven fault lines cross the Mohaka river. Most are found in the upper section but the most obvious to untrained observers is found just above a rapid called Red Rock in the grade III section. It becomes apparent a fault has been crossed as the type of rock changes almost instantly. Commercial rafting is run on all sections of

1755-472: The settlers arrived. Archeological surveys have found extensive evidence of villages and temporary camps along the lower and upper Mohaka. The Maori collected hāngī stones, taupunga, opunga, poutama, kowhaturi from the riverbed. The famous Maori, Te Kooti , reportedly frequented the area. Te Kooti's Lookout, said to be the site of a fight with the British, is visible from the river. Later, Europeans used

1800-719: The south with the Marlborough Fault System which is a large dextral strike-slip fault zone that ultimately transfers the displacement to the mainly transform plate boundary of the Alpine Fault that extends down the western South Island . To the north the North Island Fault System extends offshore on the Zealandia continental shelf and merges with the activity associated with the Kermadec-Tonga subduction zone . Active fault Active faulting

1845-422: The spring, dropping naturally throughout the summer but can rise quickly in heavy rains. Slips are common and trees can sometimes be found drifting or jammed between boulders. There is an automatic river gauge which posts water level information (NIWA) or contact the local rafting companies for current conditions. Much of the Mohaka runs through sedimentary rock . In the upper sections, greywacke commonly forms

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1890-408: The steeper banks with smaller stones and shingle forming shallow beds and beaches. Conglomerate , sandstone and limestone begin to dominate the banks and large boulders create the rapids down through the grade III section. Moving closer to the grade V section, the boulders become larger and the banks narrow into a deep gorge. Large conglomerate blocks form the first rapid then the river eases into

1935-460: The upper Mohaka, with the current one built in 1962. Ngati Pahauwera ’s traditional tribal territory is from the Te Hoe river junction to its mouth. The river, including its waters, bed and fisheries, is a taonga of Ngati Pahauwera. In particular they place great emphasis on the role the river plays in their tribal identity. The Mohaka was an important river for fishing and transport long before

1980-591: The vicinity of tectonic plate boundaries, and active fault research has focused on these regions. Active faults tend to occur less within the area of any given plate. The fact that intraplate regions may also present seismic hazards has only recently been recognized. Various geologic methods are used to define the boundaries of an active fault such as remote sensing and magnetic measurements, as well as other ways. Several types of data, such as seismologic reports or records over time, are used to gauge fault activity. Activity and fault area are correlated, and risk analysis

2025-621: Was centred near Te Mahoe , east of Kawerau . The Waiotahi Fault commences near the end of the Mangahopai Road in Hawkes Bay and extends as the most eastern active fault in the system through the western aspects of Lake Waikaremoana . It then has an eastern splay, the Koranga Fault just north of the peak Tataemakora while itself continuing all the way via the coast west of Ōpōtiki to terminate off shore where it intercepts

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