Oct 29 1995, 5:30 pm - Ruapehu Volcano

Situation Summary

As of 17:30, the following information is available:

• Significant tremor has continued to be recorded at Ruapehu on the Dome seismograph. The activity has typically occurred as numerous tremor bursts of 0.5 - 2 minutes duration. The more intense periods of activity are also recorded in an attenuated form at Whakapapa and Ngauruhoe. A discrete volcanic earthquake occurred at 16:15, followed by elevated tremor lasting for 10 - 15 minutes. Current seismic activity is at normal intra-eruption levels.

• A magnitude 4.5 tectonic earthquake occurred this morning at ~05:30, originating 70 km below Mt. Ruapehu. The earthquake was felt by residents at Ohakune.

• Observations this morning indicated moderate but semi-continuous emissions of fumes (SO₂ and other gases) from the Ruapehu crater. Visibility of the volcano has been limited by cloud for much of the afternoon preventing further observations. At present it is not known whether an ash producing eruption accompanied the 16:15 seismic event.

• At present a field party is attempting COSPEC measurements to estimate the current SO₂ flux from Ruapehu.

Conclusions and Alert Status

The present eruption episode is continuing with significant gas emissions and possible localised ash eruptions. We advise the Alert Level remains at 3.

T. Thordarson (for C.J.N. Wilson)
Volcanology Programme Manager