Report on Rabaul (Papua New Guinea) — November 1992
Bulletin of the Global Volcanism Network, vol. 17, no. 11 (November 1992)
Managing Editor: Lindsay McClelland.
Rabaul (Papua New Guinea) Fewer seismic events; uplift
Please cite this report as:
Global Volcanism Program, 1992. Report on Rabaul (Papua New Guinea). In: McClelland, L. (ed.), Bulletin of the Global Volcanism Network, 17:11. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199211-252140.
Papua New Guinea
4.271°S, 152.203°E; summit elev. 688 m
All times are local (unless otherwise noted)
"Seismic activity . . . remained at a low-moderate level during November, with 351 recorded caldera earthquakes . . . . The highest daily total of events was 36 on the 29th. Eleven earthquakes were located, distributed in the NE, N, and NW parts of the caldera seismic zone. Levelling measurements on 9 November indicated 13-16 mm of uplift at the S coast of Matupit Island since the previous measurements on 16 October. This uplift is believed to be associated with a small swarm of caldera earthquakes that occurred on 22 October. EDM measurements on 11 November indicated dilation of as much as 20 ppm in the Greet Harbor area since the previous survey, on 22 October."
Geologic Background. 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 688-m-high asymmetrical pyroclastic 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 1400 years ago. An earlier caldera-forming eruption about 7100 years ago is now considered to have originated from Tavui caldera, offshore to the north. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western 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: C. McKee, RVO.