The Poutu Fault Zone is a seismically active area of the central

North Island The North Island ( , 'the fish of Māui', historically New Ulster) is one of the two main islands of New Zealand, islands of New Zealand, separated from the larger but less populous South Island by Cook Strait. With an area of , it is the List ...

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

Geology

The intra-rift Poutu Fault Zone extends from inland of

Tūrangi Tūrangi is a small town on the west bank of the Tongariro River, 50 kilometres south-west of Taupō on the North Island Volcanic Plateau of New Zealand. It was built to accommodate the workers associated with the Tongariro Power Scheme, Tongar ...

on the shores of

Lake Taupō Lake Taupō (also spelled Taupo; or ) is a large crater lake in New Zealand's North Island, located in the caldera of Taupō Volcano. The lake is the namesake of the town of Taupō, which sits on a bay in the lake's northeastern shore. With ...

towards

Mount Ruapehu Mount Ruapehu (; English ) is an active stratovolcano at the southern end of the Taupō Volcanic Zone and North Island North Island Volcanic Plateau, volcanic plateau in New Zealand. It is northeast of Ohakune and southwest of the southern s ...

on the east side of the mountain. It has two segments known as the Poutu North fault at long and the Poutu South fault at long and 23 strands have been characterised which probably merge into a single fault plane at depth. The southern end of the Poutu North fault is in close proximity to a number of recently active vents of

Mount Tongariro Mount Tongariro (; ) is a compound volcano in the Taupō Volcanic Zone of the North Island of New Zealand. It is located to the southwest of Lake Taupō, and is the northernmost of the three active volcanoes that dominate the landscape of ...

. The northern end of the Poutu North fault essentially passes under the volcanic peak of

Pihanga Pihanga is a andesitic volcanic peak in the North Island Volcanic Plateau, located to the north of Mount Tongariro, between Tongariro and Lake Taupō. The nearest town to Pihanga is Tūrangi. Lake Rotoaira lies to the south-west 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. This is essentially a tectonic fault zone associated with about uplift in last 20,000 years making up the south eastern intra-rift faults of the Tongariro Graben in the

Taupō Rift The Taupō Rift is the seismically active rift valley containing the Taupō Volcanic Zone, central North Island of New Zealand. Geology The Taupō Rift (Taupo Rift) is a intra-arc continental rift resulting from an oblique convergence in the H ...

. Active faults in this region may well extend beyond the shore line of Lake Taupō. The nearby intra-rift Waihi fault zone to the west, by about , is parallel. The active Rotopounamu fault that has been separately named by some is now assigned to the fault zone. 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.

References

{{Seismic faults of New Zealand Seismic faults of New Zealand Taupō Volcanic Zone Tongariro Volcanic Centre Seismic zones of New Zealand