Sep 16 2002, 2:30 pm - Ruapehu Volcano

Since September 6 there have been four short-lived episodes of volcanic tremor at Ruapehu. The duration of these episodes have ranged from 8 to more than 40 hours (see plot below). Several similar episodes have been recorded this year, namely February 21 (~12 hours duration); May 17 (~24 hours) & 29 (~18 hours); June 17 (~24 hours) and July 15 (~8 hours). The earlier episodes all had similar characteristics to the recent activity.

This time, the unusual characteristic is four of these tremor episodes in a ten day period. Ruapehu Crater Lake was last visited on August 30, when the lake temperature was 19.4°C. The lake temperature has been below 20°C since mid June 2002. There have been no reports of any changes at Crater Lake. GNS volcanologists intend to visit the lake and collect water samples and further updates will be issued as necessary.

As there is no change in activity the Alert Level for Ruapehu remains at Alert Level 1.

Brad Scott
Duty Volcanologist

Plot of volcanic tremor amplitudes for 2-16 September 2002.