Turangi (Kuharua) Earthquake swarm update

Published: Tue May 30 2017 2:30 PM
Updated: Tue May 30 2017 3:30 PM

At the end of March, we reported how the swarm activity about 10 km west of Turangi (near Kuharua lava dome) had restarted with 249 locatable earthquakes occurring in the previous week.

That pulse of activity led to a M4.5 earthquake at 6 km depth the largest event to date in the sequence. This swarm has now moved into its third phase, starting last Friday 25 May. This third phase is like the second phase, just without the larger event. There have been 11 earthquakes over M3 in this phase, however none are over M3.5. To date there have been 2339 earthquakes located, 587 since Friday 25 May. The events are occurring between about 4 and 12 km depth and most are in the 5-9 km depth range. The Taupo Volcanic Zone is a rifting area, growing wider each year by 6-9 mm. These earthquakes are located on the western boundary of the Zone and are likely to be related to the long-term ‘tectonic’ stretching of the Zone. Several active faults are mapped in the GNS Science Active Faults database reflecting the ‘tectonic nature’ of this area. Currently, there are no indications that the earthquakes are related to volcanic activity, being located well away from the active volcanoes.

Plot showing the magnitude vs time for the three phases

Plot showing the magnitude vs time for the three phases

Map showing the location of known faults in the area

Map showing the location of known faults in the area

Map showing the location of the events by phase

Map showing the location of the events by phase

Earthquake swarms are a common feature of the Taupo Volcanic Zone. Every few years we have one in the greater Turangi area. This one has been ongoing since 13 February and now consists of three major pulses of activity, with about 20 days between them. The second pulse is the stronger with more events and the largest event to date. Swarms come in a variety of forms and it is not possible to judge the future easily for them. Some have the stronger phase near the start, others in the middle and some swarms have the stronger activity at the end. We still anticipate this one will continue in the short term. As usual, we continue to closely monitor the activity.