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.