Published: Fri Jan 18 2008 3:00 PM
18 January 2008, 2:00 pm - Update on Activity and Observations; Alert Level remains at Level 1
Seismic activity at Ngauruhoe increases slightly. Measurements of temperature and volcanic gas concentrations at the summit area remain normal. We have no evidence that an eruption is imminent, but will continue to monitor the volcano closely.
The Volcanic Alert Level remains at Level 1
Since our last update (1 November 2006) elevated volcanic earthquake activity has continued at Ngauruhoe. The number of events per day has typically ranged between 5 and 30 earthquakes per day. This activity started in late May 2006 and the largest earthquakes are about magnitude 1.5. Observations suggest that the earthquakes continue to occur within about 1km of the surface beneath the volcano's northern flank.On January 6 the number of events started to increase and by 9 - 10 January there were up to 80 per day, decreasing slightly since then. The magnitudes of the larger events ranged between M 1.2 and 1.5.
In response to these changes we have visited the volcano. Measurements of volcanic gas concentrations, temperatures and soil gas flux were made at the summit area of Ngauruhoe on 17 January. These data have not changed since the unrest began in late May 2006, and are similar to measurements made in 2006 - 7. The maximum fumarole temperature near the summit remains about 86°C. We have also installed 3 portable seismographs to collect more data on the continuing earthquakes.
We have recorded no other signs of unrest at Ngauruhoe, and have no evidence that an eruption is imminent. We will continue to monitor as necessary.