Seismic activity at Ngauruhoe remains elevated, although it has declined to 10 to 20 volcanic earthquakes per day from a peak of approximately 50 per day in early June. The largest earthquakes are approximately magnitude 1. Locations for the earthquakes place them 1 to 4km deep and slightly to the north or east of the summit. The accuracy of these locations is hampered by the earthquakes being very small, as they are recorded on only three or four permanent seismographs.

To help better locate the earthquakes we have installed three additional seismographs around the base of Ngauruhoe. One of the seismographs transmits data directly back to our data centres and can be monitored in real-time, while the other two seismographs record on-site and we plan to retrieve data approximately fortnightly (weather permitting). Once we have retrieved data from all sites we will attempt to refine the earthquake locations.

On 8 June we made gas and temperature measurements at the summit area of Ngauruhoe. We measured the temperature of the main fumaroles (steam vents) and collected gas samples for later analysis. The maximum fumarole temperature was 85°C, being similar to measurements in April 2006. We also sampled for carbon dioxide gas release through the soil (a gas known to be produced by degassing magma) and found no significant changes from the last measurements in May 2003. We plan to continue a subset of the gas and temperature measurements approximately fortnightly.

We have recorded no other signs of unrest. We will continue to monitor Ngauruhoe closely and will release updated information as it is available.

Alert Status

The Volcanic Alert Level remains at Level 1.

Steven Sherburn
Duty Volcanologist