The Manawahe Fault line is a seismically active area in the Bay of Plenty Region 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 ...

with the potential to be involved with other faults in an event.

Geology

North of

Lake Rotomā Lake Rotomā (also spelled Rotoma) is the fourth largest lake of the 11 lakes in the Rotorua Lakes district in the Bay of Plenty Region of New Zealand's North Island. Lake Rotomā is the easternmost in the chain of three lakes to the northeast ...

, volcanic

ignimbrite Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surrou ...

sheets from multiple eruptions of the

Ōkataina Caldera Ōkataina Caldera (Ōkataina Volcanic Centre, also spelled Okataina) is a volcano, 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 ...

extend towards the Whakatane Graben, with the volcanic region being separated from the tectonic Whakatane portion of 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 ...

by the Manawahe Fault. The fault continues to the 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 of the surface. The Manawahe Fault ruptured immediately prior to the 5500 years ago Whakatane eruption of the

and also ruptured several times, associated with the Rotoma Caldera eruptive sequence, and immediately after the Mamaku eruption.

Risks

This intra-rift fault has certainly ruptured several times in the last 10,000 years. The most recent rupture occurred 636 years ago, on a fault within the

Taupō Volcanic Zone The Taupō Volcanic Zone (TVZ) is a volcano, volcanic area in the North Island of New Zealand. It 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 n ...

that has one of the highest known slip rates, with recurrence intervals ranging from 1,580 to 2,000 years. Although potentially ruptures could be up to if the fault ruptured at the same time as the longer Matata fault, only > 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 event.

References

{{Seismic faults of New Zealand Seismic faults of New Zealand Taupō Volcanic Zone Okataina Volcanic Centre Geography of the Bay of Plenty Region Whakatane Graben