Small earthquake swarm south of Turangi

Published: Tue Sep 25 2018 10:30 AM

Our seismometer network has recorded a swarm of small earthquakes between Turangi and Lake Rotoaira over the last week.

We have located 28 earthquakes ranging in magnitude from M0.4 to 2.2 and in depth from 5-10 km. These earthquakes were too small to be widely felt – the largest event in the swarm was reported felt by only 13 people – or to cause any damage.

Time series plot showing the magnitude and depth of the earthquakes

Time series plot showing the magnitude and depth of the earthquakes

Earthquake swarms are characterised as a cluster of similar-sized earthquakes, close together in time and location, usually with no one main or large event. In this swarm the largest earthquake is near the start of the swarm on 18 September and was followed by ten smaller earthquakes, more typical of a mainshock-aftershock sequence. Then about 24 hours later, on 19 September, a further sequence occurred with the largest earthquake towards the end.

Map showing the location of the earthquakes

Map showing the location of the earthquakes

Earthquake swarms are common in this area as the Turangi-Rotoaira area forms the southern portion of the Taupo Fault Belt, a zone of faulting within the Taupo Volcanic Zone. The area is one of crustal extension, where the Taupo Volcanic Zone is getting wider. GNS Science geologists have mapped numerous active faults in the area. Many earthquakes swarms occur in this area being related to the faulting, volcanism and geothermal activity.

Map showing the active faults in the Turangi-Rotoaira area

Map showing the active faults in the Turangi-Rotoaira area