Report on Rabaul (Papua New Guinea) — August 1989
Scientific Event Alert Network Bulletin, vol. 14, no. 8 (August 1989)
Managing Editor: Lindsay McClelland.
Rabaul (Papua New Guinea) Seismicity remains at background
Please cite this report as:
Global Volcanism Program, 1989. Report on Rabaul (Papua New Guinea) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 14:8. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198908-252140
Papua New Guinea
4.271°S, 152.203°E; summit elev. 688 m
All times are local (unless otherwise noted)
"Activity remained at background level in August. The total number of caldera earthquakes was 202. All of these events were small (ML <1.5). The 14 that could be located occurred in two clusters; one in the Matupit Island/Greet Harbour area, and the other in the S part of the caldera seismic zone. Ground deformation measurements showed no significant trends."
Geological Summary. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor utilized by what was the island's largest city prior to a major eruption in 1994. The outer flanks of the asymmetrical shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the east, where its floor is flooded by Blanche Bay and was formed about 1,400 years ago. An earlier caldera-forming eruption about 7,100 years ago is thought to have originated from Tavui caldera, offshore to the north. Three small stratovolcanoes lie outside the N and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and W caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city.
Information Contacts: I. Itikarai and C. McKee, RVO.