Earthquake swarm activity highlights crustal faulting associated with the Waimangu–Rotomahana–Mt Tarawera geothermal field, Taupo Volcanic Zone

• Sporadic earthquake swarms have been recorded near Waimangu–Rotomahana since the early 1990s.
• These swarms are often just 4 to 8 h in duration.
• Well-relocated earthquakes highlight a ~ 6 km long NE–SW lineation.
• The inferred fault may act as a permeable pathway for fluid and CO2 migration.

The Waimangu–Rotomahana–Mt.Tarawera geothermal field (WRTGF) in the Taupo Volcanic Zone, New Zealand, experiences frequent but sporadic earthquake swarms with durations of less than 1 day. Here we examine detailed locations of the seismic activity using precise double-difference relative location techniques. We utilize a combination of cross-correlation-derived arrival times and catalogue-based arrival times from 582 earthquakes recorded in the area between 2004 and 2015 for the relocation analysis. The new earthquake locations highlight a ~ 6 km long NE–SW lineation, which we infer to represent a sub-surface fault that extends along the northern side of Waimangu geothermal system and the north-western end of Lake Rotomahana. We suggest that this structural feature acts as a permeable pathway for aqueous fluid and CO2 release up to the surface geothermal field and Lake Rotomahana, from a deeper magmatic source.