Manawahe Fault

North of Lake Rotomā, 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 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 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]

This intra-rift fault has certainly ruptured several times in the last 10,000 years.^[2] The most recent rupture occurred 636 years ago, on a fault within the Taupō Volcanic Zone that has one of the highest known slip rates, with recurrence intervals ranging from 1,580 to 2,000 years.^[1] Although potentially ruptures could be up to M_w 7 if the fault ruptured at the same time as the longer Matata fault, only > M_w 5.5 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 M_w 6.3event.^[1]