| Whangamata fault zone | |
| Other Name: | Whangamata Fault, Haukari/West Whangamata Fault [1] |
| Named For: | Whangamata Bay, Lake Taupō |
| Pushpin Relief: | 1 |
| Country: | New Zealand |
| Region: | Waikato Region |
| Coordinates: | -38.588°N 175.962°W |
| Plate: | Indo-Australian |
| Status: | Active |
| Earthquakes: | June - July 1922, 2001 |
| Type: | Normal fault |
| Movement: | 5 MW+ in 1922 with 1.8m (05.9feet) displacement[2] |
| Age: | Quaternary |
| Volcanic Arc/Belt: | Taupō Volcanic Zone |
| Embed: | New Zealand geology database (includes faults) |
The Whangamata fault zone is part of the seismically active western Taupō rift-bounding normal wall faults [1] and is associated with the major active Whangamata Fault and Haukari/West Whangamata Fault and several unnamed active faults. Obsidian used by the Māori is exposed along these faults.[3]
The known active faults in the zone extend north east from Kinloch on the north west shore of Lake Taupō approximately through the rhyolytic volcanic dome of Ben Lomond[4] to the region of the Mokai Power Station.
The present western wall faults of the Taupō Fault Belt in this region of active extension by 8mm/year ± 2mm[1] of the modern Taupō Volcanic Zone have been defined by earthquake swarms such as occurred in 1922 which resulted in a 1.8m (05.9feet) displacement of the Whangamata Fault[2] and the swarm of 2001.[5] To the north the zone continues as the Thorpe - Poplar Fault and to the south has its structure disturbed and hidden by the Taupō Volcano. The 2001 earthquake swarm is best explained by intrusion into a volcanic dyke.[5]
These are typical for a fault structure adjacent to an active volcanic caldera filled with a lake, being both tectonic and any associated volcanism and so could be significant. The 1922 earthquake swarm was associated with several earthquakes in the range of 5 to 5.4 MW which caused chimney collapse, land slips, as well as both local and international concern sufficient to impact the tourist industry given the manifest lake shore subsidence and fault displacements.[2] The swarm lasted nine months with total displacement of up to on the northern shore of Lake Taupō (not just the Whangamata fault zone was involved).[2] As the magma-tectonic interaction of the 2001 swarm may have been from a magma source independent of the Taupō Volcano, relatively small scale eruption associated with the faults would be possible, if a dyke reaches the surface.[5]
The extensive and used obsidian outcrops near Kinloch were accessible to the Māori as they were exposed by the Whangamata Fault.[3]