Taupō Rift Termination Faults

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 (Desert Road 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 magnitude.

The faults can be classified as belonging to three normal fault sets:
# Ruapehu Graben NNE‐trending faults
#* Raurimu Fault - see separate article
#* Rangipo Fault (Desert Road Fault) - see separate article
#* Mostly uncharacterised faults under Mount Ruapehu
# Ohakune‐Raetihi fault set that is wide of E‐W to ESE‐WNW‐trending faults
#* Ohakune Fault
#* Raetihi North and South faults
#* Waipuna Fault
#* Oruakukuru Fault
#* Rangiahu Fault
#* Maketu Stream Fault (Maketu Trace)
# Karioi fault set that is wide of NE‐trending faults
#* Karioi Fault
#* Wahianoa Fault
#* Snowgrass Fault
#* Shawcroft Road Fault
#* Moawhango Fault

Ohakune Fault

This most northerly of the cross faults extends from northwest of Tohunga Junction into the Rangataua Forest. At Tohunga Junction it crosses the Raurimu Fault with a complex series of faults. The fault to the west of this junction region has of vertical displacement and to the east there is only . This downthrown to the south normal fault has been active for over 18,000 years and has a dip-slip displacement rate of /year.

The Ohakune volcanic complex (Rochfort ejecta ring and craters) which erupted about 31,500 years ago is situated on and aligned with the fault just north of the town.

Raetihi faults

The E - W trending of the Raetihi North Fault is downthrown to the south while the Raetihi South Fault is downthrown to the north so they have a small graben between them. The Raetihi South Fault possibly continues along the Mangahowhi Stream for up to . Displacement rates based on an age of 18,000 years for the scarps are /year for the Raetihi North Fault and /year for the Raetihi South Fault.

Waipuna Fault

South of the Raetihi faults, the most western of the faults discussed, the Waipuna Fault is downthrown to the south and extends from the Waimarino Forest to intersept the Karioi Fault. The displacement rate might be /year but this has an error of the same order.

Oruakukuru Fault

The Oruakukuru Fault to the south of the Waipuna Fault commences at State Highway 4 (New Zealand) close to the upper Mangawhero River extending also intersects the Karioi Fault and has a displacement rate of /year.

Snowgrass Fault

The south east Taupō Rift is associated with a northeast trending dome south of the Ngamatea Swamp where the Rangipo Fault terminates. The
Snowgrass Fault on the northern side of this dome is a downthrown to the south normal fault that is displacing at an estimated /year.

Shawcroft Road Fault

The Shawcroft Road Fault cuts across the Rangipo Fault line just to the north east of the Waiouru Military Camp and is displacing at /year.

Karioi Fault

The normal Karioi Fault is parallel and to the north of the Shawcroft Road Fault and is long with a summed displacement for its two strands of /year.

Wahianoa Fault

The Wahianoa Fault is a northeast-striking presumed normal fault across the southeast flank of Mount Ruapehu extending at least from the Ohakune Fault towards the Rangipo Fault and the Upper Waikato Stream Fault with a displacement rate of /year.
It has been postulated that it has the potential to do a whole fault rupture at the same time as whole fault rupture of the Rangipo and Upper Waikato Stream faults which would result in a event rupturing by an average of

References

{{Seismic faults of New Zealand

Seismic faults of New Zealand
Taupō Volcanic Zone
Tongariro Volcanic Centre
Ruapehu District
Seismic zones of New Zealand