Rabaul Update: October 3, 1994
Summary of telephone conversation between CVO staff and the USGS/VDAP team at the Rabaul Volcano Observatory.
- Tom Murray stated the VDAP team arrived in Rabaul on 30 September without problems, that all of
their equipment arrived intact, and that things are going well for them at Rabaul.
- Eruptive activity continues to decline. Eruptive activity at Vulcan has essentially stopped.
Tavurvur continues to erupt, but at a low level of activity. There is a constant plume up to an altitude
of about 1 km. Occasional explosions eject debris to altitudes of about 400 m above the vent. Overflights
during occasional periods of decreased activity have allowed views into the Tavurvur crater where a small
lava flow less that about 200 m in length has been observed.
- Seismicity in Rabaul caldera is low and has almost reached pre-eruption background levels.
Scientists at RVO are puzzled about the low level of seismic activity; they expected to see more
high frequency earthquakes as a result of structural adjustments to the eruption.
- Deformation is still continuing. Matupit Island has experienced about 60 microradians of
deflation during the last week and is still deflating at about 10 microradians per day (tilt-leveling data).
Deformation in the form of inflation near Matupit Island was observed during the night shortly before
the beginning of the eruptions, when a tide gauge was observed uplifted out of the water. RVO staff
indicate that no unusual deformation was observed 7 days before the eruption.
- The VDAP team reported observing a pumice raft in Rabaul harbor that extends from the harbor
shore at Rabaul town south to the south end of Vulcan.
- The VDAP team reported that RVO has only four seismic stations operating; three of the original
net stations and a new one installed yesterday in the basement of RVO. The new Willie Lee data acquisition
and analysis system is up and operating but seismic events cannot yet be located with the present net
(too few stations and bad geometry). The RVO and VDAP staff plan to install a new seismic station and
a tiltmeter on Matupit Island today and other stations in the near future. The team hopes to be able
to locate events within a couple of days. Most seismic-station sites will be reached by ground vehicle
rather than by helicopter.
- Rabaul town is still pretty much evacuated and visitors need a permit to enter the town. Andy
Lockhart reports that there is about 6 inches of ash in the northern part of Rabaul Town and that about
10-20% of the structures are destroyed. The eastern part of Rabaul is covered by about 1.5 to 2 feet
of ash and nearly 100% of the buildings are seriously damaged or destroyed. Areas south of the airport
near Matupit Island have less ash and about 20% of buildings are destroyed.