During the last three weeks there has been a significant change in the number and magnitude of low frequency earthquakes being recorded by seismographs around Mt Ngauruhoe.

Initial analysis indicates these earthquakes are occurring about 4km deep beneath Ngauruhoe, but they could be shallower.

Earthquakes of this type are commonly interpreted as being related to the movement of magmatic fluids (magma itself and/or volcanic gases).

This increase in earthquake activity does not necessarily mean that an eruption is imminent.

The last significant eruption at Ngauruhoe was in 1975. There was minor seismic activity in 1983, 1991, 1994 and 1995, but otherwise Ngauruhoe usually has little earthquake activity.

We plan to carry out additional monitoring at Ngauruhoe in the coming week that will help us better define the nature of the activity. Initially this will consist of gas sampling and deployment of portable seismographs.

We will continue to monitor Ngauruhoe closely and will release updated information as it is available.

Alert Status

The seismic activity around Ngauruhoe has increased above the typical background level so the Volcanic Alert Level is raised to Level 1.

Michael Rosenberg
Duty Volcanologist