Manawahe Fault

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Manawahe Fault
Manawahe Fault
Approximate surface traces of the active Manawahe Fault in red in the Taupo Rift, North Island, New Zealand {{cite web|url=https://data.gns.cri.nz/af/ | title=GNS:New Zealand Active Faults Database|access-date=2023-04-07}}
Etymology Manawahe
Coordinates 37°57′50″S176°40′16″E / 37.964°S 176.671°E / -37.964; 176.671
Country New Zealand
RegionBay of Plenty Region
Characteristics
Range Mw 6.3 [1]
Length14 km (8.7 mi) [1]
Strike ENE [1]
Displacement 3 mm (0.12 in)/yr [1]
Tectonics
Plate Indo-Australian
Status Active, recurrence is 1580–2000 years [1]
Type Normal fault [1]
Age Holocene ~0.1  Ma
O
S
D
C
P
T
J
K
Pg
N
Volcanic arc/belt Taupō Volcanic Zone
New Zealand Active Fault database

The Manawahe Fault line is a seismically active area in the Bay of Plenty Region of the central North Island of New Zealand with the potential to be involved with other faults in an Mw 7.0 event. [1]

Contents

Geology

North of Lake Rotoma, volcanic ignimbrite sheets from multiple eruptions of the Ōkataina Caldera extend towards the Whakatane Graben with the volcanic region being separated from the tectonic Whakatane portion of the Taupō Rift by the Manawahe Fault. [1] The fault continues to east and coast in the Matata Fault line. The Manawahe Fault consists of a series of closely-spaced, mainly SSE-dipping fault traces, which are parallel to the North Rotoma Fault at the edge of the north eastern edge of the Rotoma Caldera. The traces are presumed to merge within 3 km (1.9 mi) of the surface. [1] The Manawahe Fault ruptured immediately prior to the 5500 years ago Whakatane eruption of the Ōkataina Caldera and also ruptured several times, associated with the Rotoma Caldera eruptive sequence, and immediately after the Mamaku eruption. [1]

Risks

This intra-rift fault has certainly ruptured several times in the last 10,000 years. [2] The last rupture identified was 636 years ago, with recurrence intervals between 1580–2000 years of a fault with one of the highest slip rates so far defined in the Taupō Volcanic Zone. [1] Although potentially ruptures could be up to Mw7 if the fault ruptured at the same time as the longer Matata fault, only > Mw5.5 can be definitely assigned on displacements characterised to date as there appears to have never been a single full length fault rupture which would result in a Mw6.3event. [1]

Related Research Articles

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<span class="mw-page-title-main">Mount Tarawera</span> Volcano in New Zealand

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<span class="mw-page-title-main">Horohoro Fault</span>

The Horohoro Fault is in the old Taupō Rift of the central North Island of New Zealand.

The Taupō Fault Belt contains many almost parallel active faults and is located in the Taupō Rift of the central North Island of New Zealand geographically between Lake Taupō and the lakes of Rotorua, Tarawera, Rotomahana and Rerewhakaaitu. The Waikato River bisects the western region of the belt.

Much of the volcanic activity in the northern portions of the North Island of New Zealand is recent in geological terms and has taken place over the last 30 million years. This is primarily due to the North Island's position on the boundary between the Indo-Australian and Pacific Plates, a part of the Pacific Ring of Fire, and particularly the subduction of the Pacific Plate under the Indo-Australian Plate. The activity has included some of the world's largest eruptions in geologically recent times and has resulted in much of the surface formations of the North Island being volcanic as shown in the map.

The Rotoiti Caldera is a postulated, mainly infilled sub caldera of the Ōkataina Caldera based upon gravitational and magnetic evidence. It erupted 100 cubic kilometres (24 cu mi) of magma that is used in the recent stratigraphy of much of the northern North Island. It was formed in the larger paired eruption with the lesser Earthquake Flat vents linked by tectonic interaction across the length of the Ōkataina Caldera. The series of eruptions was about 50,000 years ago, with the resulting widespread Rotoiti ignimbrite and several layers of Rotoiti/Rotoehu tephra/brecca/ash giving challenges in consistent dating. It was subsequently infilled by later eruptive activity to a depth of over 2 km (1.2 mi). The paired eruptions may have erupted about 240 cubic kilometres (58 cu mi) of tephra.

The Whakatāne Graben is a predominantly normal faulting tectonic feature of the northeastern most aspect of the young, modern Taupō Rift in New Zealand. At the coast it is widening by about 7 mm (0.28 in)/year. This very geologically active graben was the site of the 1987 Edgecumbe earthquake, which caused up to 2 m of land subsidence. The discontinuity in the Taupō Volcanic Zone's faults imposed by the highly active Ōkataina Volcanic Centre, geography and geology mean the graben includes the actively expanding and lowering region onshore extending towards the coast, but some scientists have used the term to refer to only the offshore continuation of the Taupō Rift.

The Matata Fault zone is a seismically active area in the Bay of Plenty Region of the central North Island of New Zealand with potential to rupture as part of an Mw 7.0 event.

The Rangipo Fault is the eastern Taupō rift-bounding north–south striking normal fault complex of the Ruapehu Graben, a seismically active area of the central North Island of New Zealand to the west of Mount Ruapehu. It could be part of a Mw7.1 potential rupture.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 Villamor, P.; Litchfield, N.J.; Gomez, D.; Martin, F.; Alloway, B.; Berryman, K.; Clark, K.; Ries, W.; Howell, A.; Ansell, B. (2022). "Fault ruptures triggered by large rhyolitic eruption s at the boundary between tectonic and magmatic rift segments: the Manawahe Fault, Taupo Rift, New Zealand". Journal of Volcanology and Geothermal Research. doi:10.1016/j.jvolgeores.2022.107478.
  2. Berryman, Kelvin; Villamor, Pilar; Nairn, Ian; Begg, John; Alloway, Brent V.; Rowland, Julie; Lee, Julie; Capote, Ramon (2022). "Volcano-tectonic interactions at the southern margin of the Okataina Volcanic Centre, Taupō Volcanic Zone, New Zealand". Journal of Volcanology and Geothermal Research. 427 (107552). doi:10.1016/j.jvolgeores.2022.107552. ISSN   0377-0273.