Ruapehu - IGNS - Science Alert Bulletin V95/32

Friday 6 October 1995
1800 hours NZDT (UT  +13)
Ruapehu Volcanic Activity

Situation Summary

As of 1800 hours the situation is as follows.

*    Following an eruption earthquake at 1128 on 5 October the level of
volcanic seismicity has increased, and has since remained at a higher
level.

*    Four volcanic eruption earthquakes have been recorded in the past 30
hours:

5 October 1128: M3.0, with ashfall at Karioi Forest and Waiouru
5 October 2326: M3.1, no eruption observations known
6 October 0629: M3.1, eruption column to 23 000-25000 feet (approx. 7000m), 
                ashfall onto Desert Road area.
6 October 1055: M3.2, small lahar reported in Whangaehu River, eruption 
                column to >27 000 feet (approx. 8000 m).

     A general increase in volcanic tremor has followed the 1128 eruption
on 5 October, with periods of relatively strong low frequency tremor being
recorded on the Chateau and Ngauruhoe seismographs during today.

*    Weather conditions have prevented views of Ruapehu summit today. A
helicopter inspection during the afternoon found no ash on the eastern
slopes of the volcano, where fresh snow has fallen.

*    The only Institute field parties working at the volcano today
serviced the portable seismic equipment.

Conclusions and Alert status

Intermittent explosive eruptions are continuing from the volcano.  The
reappearance of low frequency tremor may indicate the likely continuation
of magma movement at depth, with consequent eruptive activity at the
volcano.

The Alert Level remains at 3.

IA Nairn for
Dr CJN Wilson, Programme Leader, Volcanology