Rabaul Update: October 3, 1994

• 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.