Earthquake swarm in the Taupō Volcanic Zone, New Zealand

lake taupo earthquake swarm april to may 2022

The GeoNet earthquake monitoring network has recorded a small swarm of earthquakes at Lake Taupō, New Zealand over the last 2 to 3 weeks. Lake Taupō is a large caldera volcano, a special type of volcano that has rare but unusually large eruptions.

  • Such swarms are normal and several are recorded each year.
  • The last supereruption at Taupo took place some 26 000 years ago, producing about 1 170 km3 (281 mi3) of tephra and covering North Island in debris up to 200 m (660 feet) deep. 
  • This was the largest volcanic eruption on Earth in the past 70 000 years.

GeoNet earthquake monitoring network has located more than 84 earthquakes under Lake Taupō since April 28, 2022, with only two of these being over M3.1

Earthquakes in the Lake Taupō area are typically shallower than 15 km (9 miles), and the recent events are no different, with depths ranging from 3 – 16 km (1.8 – 10 miles).

lake taupo earthquake swarm april to may 2022 bg
Earthquakes reported at Lake Taupo from April 17 – May 18, 2022. Credit: GeoNet

The recent earthquake activity has been grouped in two places under the lake.

A cluster trending NE-SW along the east shore and a cluster in the middle of the lake.

There have also been earthquakes to the north, around the Wairakei geothermal system. Only a few of the larger quakes in this sequence have been felt locally.

Earthquake swarms are common in the Taupō Volcanic Zone (TVZ), and several are recorded each year, GeoNet scientists said.

The swarms can be related to the active faults in the TVZ and volcanic processes at the caldera volcanoes like Taupō and Okataina.

Larger ones have lasted weeks-to-months and can include many hundreds of earthquakes.

“In the last 10 years we have located over 4 200 earthquakes under Lake Taupō. These are part of the activity that defines the background level of unrest for Taupō Volcano,” GeoNet said.

The recent earthquakes are in a similar location to a series of earthquakes in 2019 that were studied in detail by the ECLIPSE program. The results of the study showed that earthquakes are related to the margins of the hot mush zone under the volcano and are signs that Taupō volcano is active.

Variations in the level of background unrest are common for caldera volcanoes like Taupō.

A research article published by AGU on June 7, 2021, shows that unrest registered under Taupo in 2019 was volcanic in nature and origin, demonstrating that it’s still an active and potentially hazardous volcano that needs to be carefully monitored.2

Geological summary

Taupo, the most active rhyolitic volcano of the Taupo volcanic zone, is a large, roughly 35 km (21 miles) wide caldera with poorly defined margins. It is a type example of an “inverse volcano” that slopes inward towards the most recent vent location.

The caldera, now filled by Lake Taupo, largely formed as a result of the voluminous eruption of the Oruanui Tephra about 22 600 years before present (BP).

This was the largest known eruption at Taupo, producing about 1 170 km3 (281 mi3) of tephra. This eruption was preceded during the late Pleistocene by the eruption of a large number of rhyolitic lava domes north of Lake Taupo.

Large explosive eruptions have occurred frequently during the Holocene from many vents within Lake Taupo and near its margins.

The most recent major eruption took place about 1 800 years BP from at least three vents along a NE-SW-trending fissure centered on the Horomotangi Reefs. This extremely violent eruption was New Zealand’s largest during the Holocene and produced the thin but widespread phreatoplinian Taupo Ignimbrite, which covered 20 000 km2 (7 722 mi2) of North Island.3

References:

1 Earthquake swarm under Lake Taupō – GeoNet – May 20, 2022

2 Analysis of 2019 unrest at Taupō supervolcano shows it was volcanic in nature and origin, calls for careful monitoring – The Watchers – June 23, 2021

3 Taupo – Geological summary – GVP

Featured image credit: GeoNet

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