The U.S.G.S./Cascades Volcano Observatory Rabaul Response

Elliot Endo, Andrew Lockhart, and Thomas Murray

On Wednesday, September 28, 1994, a 3-person team from the U.S. Geological Survey (USGS) Cascades Volcano Observatory (CVO) in Vancouver departed from Portland airport, Oregon, with equipment contained in 48 pieces of checked baggage to help restore the volcano monitoring capability of the Rabaul Volcano Observatory (RVO) on the island of New Britain, Papua New Guinea. The USGS/CVO team was responding to an official request by the Papua New Guinea (PNG) government via the U.S. Agency for International Development (USAID)/Office of Foreign Disaster Assistance (OFDA). The response was funded by USAID/OFDA through the Volcano Disaster Assistance Program (VDAP). The team arrived in Port Moresby, PNG, in the early evening of Friday, September 30. The following day, Saturday, October 1, our equipment as well as humanitarian aid was transported to Tokua airport (backup airstrip for Rabaul), New Britain via U.S. Air Force C-130. Rod Stewart, the RVO staff seismologist, met the USGS team at the Tokua airstrip with vehicles for transporting the team and equipment to RVO. During the period from October 2 to October 16, with the assistance of RVO personnel, 8 radio telemetering seismic stations and 2 radio telemetering tiltmeters were installed in the Rabaul caldera area. For the purpose of recording and analyzing seismic and tilt data, 7 personal computers ranging from laptops to 486-33 desktops were installed at the observatory. The seismic network operated by RVO prior to the eruption was almost completely out of commission owing to eruptive activity and vandalism. The primary goals of the USGS response were to provide RVO with the capability to quickly locate local earthquakes, to accurately track the background level of seismic activity by continuous amplitude measurements of select seismic signals, and to monitor deformation ground tilt in real-time. The restored seismic network and telemetering tiltmeter stations will allow RVO to provide real-time volcanic hazard assessments to civil authorities as the town is re-built and re-occupied.

RVO and the USGS team chose to first install a seismic station on Matupit island a few kilometers from the erupting volcano, Tavurvur, and to recover an old telemetering tiltmeter site on the island. The first new seismic station and telemetering, tiltmeter were operational on October 4. The work on Matupit island gave us the first opportunity to view Tavurvur closeup. At 2 km distance the view of eruptive activity at Tavurvur was impressive. At intervals of a few minutes there were explosive bursts of fume and ash from Tavurvur accompanied by jet aircraft exhaust-like sounds.

During our first week at Rabaul, most of the ballistic ejecta from Tavurvur was confined to the limits of the summit crater. About a week later, ejecta was being found beyond the base of the cone and evening views of explosive activity with incandescent ejecta were spectacular. At about 0645 am on October 14, alerted by a sonic boom-like explosion sound, we witnessed car size ejecta falling about 1 km west and south of Tavurvur in Greet (Matupit) harbor. Ejecta falling in the of Sulphur Point area started a fire at the edge of a coconut grove.

When we arrived at RVO on October 1, there was still a few inches of ash remaining on the ground. Louvered windows on most homes readily passed the ash into homes. A high priority at RVO was ash removal from the observatory roof and from the roofs of staff homes. Down spouts from the roofs to cisterns were disconnected to preserve existing water supplies. Since the prevailing wind direction was from SE to NW it was common for RVO to be in the plume from Tavurvur. Ash fall was light and fumes were tolerable.

The exact economic impact of the effects of the volcano on Rabaul is not known yet. during our stay Rabaul was still considered to be a disaster area and was in the early stages of salvage and cleanup. A substantial number of homes and businesses were severely damaged by collapsed roofs and flooding. The south and eastern parts of the city were covered by almost a meter of ash. Further damage from mudflows is expected during the rainy season.

On Saturday, October 15, with the response goals met, 2 members of the USGS team took the opportunity to depart from Tokua airport for Port Moresby via a Royal Australian Air Force C-130 (via Lae and Girua). On Monday October 17, the third member of the team arrived in Port Moresby via scheduled commercial aircraft. We all arrived at the Portland airport on October 20 after a postponed departure (1 day) from Sydney.

A followup visit to Rabaul by VDAP personnel is planned for late 1994 or early 1995 to evaluate the performance of volcano monitoring equipment installed, maintenance, and additional training if required.