Poutu Fault Zone

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Poutu fault zone
Turangi1b.jpg
North western most faults associated with the Poutu Fault Zone are in this view to northeast towards the Motuoapa Peninsula. A fault strike of the Rotopounamu Fault on the lakeside flats with the Motuoapa Peninsula beyond which also has an unnamed fault exist as on map below but are not obvious.
Poutu Fault Zone
Known active Pouto Fault Zone surface traces.'"`UNIQ--ref-00000002-QINU`"''"`UNIQ--ref-00000003-QINU`"' For map of other nearby active faults see Taupō Rift.
EtymologyMaori for elevation above others, mountain, column or pole
Coordinates 39°05′S175°48′E / 39.09°S 175.8°E / -39.09; 175.8
Country New Zealand
Region Waikato Region
Characteristics
RangeUp to 6.9 Mw
Length30 km (19 mi)
Strike N-S
Displacement 2.2 mm (0.087 in)/yr±1.9 mm (0.075 in)/yr [1]
Tectonics
Plate Indo-Australian
Status Active
Type Normal fault
Age Miocene-Holocene
Volcanic arc/belt Taupō Volcanic Zone
New Zealand geology database (includes faults)

The Poutu Fault Zone is a seismically active area of the central North Island of New Zealand.

Contents

Geology

The intra-rift Poutu Fault Zone extends 30 kilometres (19 mi) from inland of Tūrangi on the shores of Lake Taupō towards Mount Ruapehu on the east side of the mountain. It has two segments known as the Poutu North fault at 18 kilometres (11 mi) long and the Poutu South fault at 12 kilometres (7.5 mi) long and 23 strands have been characterised which probably merge into a single fault plane at depth. [1] The southern end of the Poutu North fault is in close proximity to a number of recently active vents of Mount Tongariro. The northern end of the Poutu North fault essentially passes under the volcanic peak of Pihanga. Accordingly there is the potential for both active faulting and magmatic processes to trigger earthquakes. The relative proportions contributed is important for determining earthquake associated risk and previous assumptions about magmatic processes being dominant are not the case. However magmatic activity is associated with higher earthquake activity and increased slippage rate. [2] This is essentially a tectonic fault zone [2] associated with about 65 m (213 ft) uplift in last 20,000 years [3] making up the south eastern intra-rift faults of the Tongariro Graben in the Taupō Rift. Active faults in this region may well extend beyond the shore line of Lake Taupo. [4] The nearby intra-rift Waihi fault zone to the west, by about 10 kilometres (6.2 mi), is parallel. [5] The active Rotopounamu fault that has been separately named by some is now assigned to the fault zone. [2] [4] The Poutu fault zone to the south appears discontinuous to the active faults on the eastern side of the Ruapehu graben.

Risk

Up to magnitude 6.9 earthquakes might occur with a mean of 6.6 about every 550 years along the fault. [1]

Related Research Articles

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The Taupō Volcanic Zone (TVZ) is a volcanic area in the North Island of New Zealand that has been active for at least the past two million years and is still highly active. Mount Ruapehu marks its south-western end and the zone runs north-eastward through the Taupō and Rotorua areas and offshore into the Bay of Plenty. It is part of a larger Central Volcanic Region that extends to the Coromandel Peninsula and has been active for four million years. The zone is contained within the tectonic intra-arc continental Taupō Rift and this rift volcanic zone is widening unevenly east–west with the greatest rate of widening at the Bay of Plenty coast, the least at Mount Ruapehu and a rate of about 8 mm (0.31 in) per year at Taupō. The zone is named after Lake Taupō, the flooded caldera of the largest volcano in the zone, the Taupō Volcano and contains a large central volcanic plateau as well as other landforms.

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

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<span class="mw-page-title-main">Kapenga Caldera</span> Volcanic caldera in New Zealand

The Kapenga Caldera in New Zealand’s Taupō Volcanic Zone lies in a low land area immediately south of Lake Rotorua through the Hemo Gap in the Rotorua Caldera rim. At some time more than 60,000 years ago Lake Rotorua drained through the Hemo Gap and some of the Kapenga Caldera floor was likely occupied by a lake, that has been called Kapenga.

<span class="mw-page-title-main">Ōkataina Caldera</span> Volcanic caldera in New Zealand

Ōkataina Caldera is a volcanic caldera and its associated volcanoes located in Taupō Volcanic Zone of New Zealand's North Island. It has several actual or postulated sub calderas. The Ōkataina Caldera is just east of the smaller separate Rotorua Caldera and southwest of the much smaller Rotomā Embayment which is usually regarded as an associated volcano. It shows high rates of explosive rhyolitic volcanism although its last eruption was basaltic. The postulated Haroharo Caldera contained within it has sometimes been described in almost interchangeable terms with the Ōkataina Caldera or volcanic complex or centre and by other authors as a separate complex defined by gravitational and magnetic features.. Since 2010 other terms such as the Haroharo vent alignment, Utu Caldera, Matahina Caldera, Rotoiti Caldera and a postulated Kawerau Caldera are often used, rather than a Haroharo Caldera classification.

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<span class="mw-page-title-main">Waihi Fault Zone</span> Fault zone in New Zealand

The Waihi Fault Zone is a seismically active area of the central North Island of New Zealand whose earthquakes have been associated with significant loss of life.

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The Paeroa Fault is a seismically active area in the Taupō District, Waikato Region of the central North Island of New Zealand.

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

The Ngapouri-Rotomahana Fault is a seismically and volcanically active area of the central North Island of New Zealand.

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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 Mw7.0 event.

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 National Park Fault is the western Taupō rift-bounding NNE-striking normal fault complex of the Tongariro Graben, a seismically active area of the central North Island of New Zealand south of Lake Taupō that contains Mount Tongariro.

The Raurimu Fault is the western 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.

The seismically active southern end of the Taupō Rift beyond Mount Ruapehu has a number of mainly east to west orientated termination faults where the western wall Raurimu Fault and eastern wall Rangipo Fault terminate in the Ruapehu Graben, of the central North Island of New Zealand. In a multi-fault rupture event there is the potential for the earthquake being of Mw7.1 magnitude.

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.

The Upper Waikato Stream Fault is an eastern Taupō rift-bounding north–south striking normal fault in the Ruapehu Graben, a seismically active area of the central North Island of New Zealand to the west of Mount Ruapehu. While its own whole fault rupture potential is Mw6.5, such a rupture could be part of a Mw 7.1 multi-fault rupture.

References

  1. 1 2 3 Gómez‐Vasconcelos, Martha; Villamor, Pilar; Procter, Jon; Palmer, Alan; Cronin, Shane; Wallace, Clel; Townsend, Dougal; Leonard, Graham (2018). "Characterisation of faults as earthquake sources from geomorphic data in the Tongariro Volcanic Complex, New Zealand" (PDF). New Zealand Journal of Geology and Geophysics. doi:10.1080/00288306.2018.1548495.
  2. 1 2 3 Gómez‐Vasconcelos, Martha; Villamor, Pilar; Cronin, Shane; Procter, Jon; Palmer, Alan; Townsend, Dougal; Leonard, Graham (2017). "Crustal extension in the Tongariro graben, New Zealand: Insights into volcano-tectonic interactions and active deformation in a young continental rift" (PDF). Geological Society of America Bulletin. 129 (9–10). doi:10.1130/B31657.1.
  3. Heinrich, Mirja; Cronin, Shane J.; Pardo, Natalia (2020). "Understanding multi-vent Plinian eruptions at Mt. Tongariro Volcanic Complex, New Zealand". Bulletin of Volcanology. 82 (30). doi:10.1007/s00445-020-1369-7.
  4. 1 2 "Active fault mapping in the south western bays (Pukawa, Omori, Kuratau) of Lake Taupō: Response to requests 2021" (PDF). Retrieved 19 April 2023.