Taupo, like Rotorua, Reporoa, Ngakuru and Turangi, lies within the area called the Taupo Volcanic Zone. This is an area where many large caldera volcanoes and geothermal systems are present and is also an area where small earthquakes are frequent. The earthquakes often occur as swarms. Earthquake swarms are defined as a sequence of many earthquakes striking in a relatively short period of time in a localised area. They are differentiated from ‘normal’ earthquakes followed by aftershocks by the fact that no single earthquake in the sequence is obviously the main shock. The larger or largest event can come early in the sequence towards the middle or at the end. The rate that earthquakes occur can also vary through the sequence.

The residents of Taupo often feel small earthquakes and Tuesday afternoon was no different. Two small events, 2 minutes apart were widely felt locally. The earthquakes were small (under M2.3), shallow and located to the north of Centennial Park. Around 200 people reported each event. Small earthquakes are very common in this area and tend to cluster about the Wairakei-Tauhara and Rotokawa geothermal areas. Some also occur out in the lake area. In the last year GeoNet has recorded and located 152 events. Only four of them are larger than M3; the largest event is M4 and occurred at 10.12 pm on 2 January 2017 near Rotokawa.

The residents of the Turangi-Waihi-Pukawa-Omori area have also been experiencing earthquakes over the last few weeks. A swarm has been on going to the west of there since Monday 13 February. To date GeoNet has recorded and located 587 earthquakes in this swarm, the largest event is a M3.8 on 21 February at 9.35 pm. There have only been four events larger than M3 in the swarm. The number of events per day is slowly declining and only 52 were located in the last week. The events are occurring between about 4 and 10 km depth and most are smaller than M2 (550 of the 587 to date). The Taupo Volcanic Zone is a rifting area, growing wider each year by 6-9 mm. These earthquakes are located on the western boundary and are likely to be related to the long-term ‘tectonic’ stretching of the Zone. Currently, there are no indications that the earthquakes are related to volcanic activity, being located well away from the active volcanoes. As usual, we continue to closely monitor the activity.