Report on Rabaul (Papua New Guinea) — March 1994
Bulletin of the Global Volcanism Network, vol. 19, no. 3 (March 1994)
Managing Editor: Richard Wunderman.
Rabaul (Papua New Guinea) Seismicity declines slightly; three earthquake swarms
Please cite this report as:
Global Volcanism Program, 1994. Report on Rabaul (Papua New Guinea). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 19:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199403-252140.
Papua New Guinea
4.271°S, 152.203°E; summit elev. 688 m
All times are local (unless otherwise noted)
"Seismicity declined slightly in March. The total number of recorded caldera earthquakes was 458 . . . . Three small earthquake swarms occurred. The first two, on 9 March, were located in Greet Harbour and near the airport; a total of 53 earthquakes were recorded that day. The other swarm consisted of 123 earthquakes on 13 March in the Karavia Bay area. During the month, 46 earthquakes were located instrumentally, 17 of them with reasonable errors (<1 km). Locations were mainly in Greet Harbour, the airport region, and ~1 km E of Vulcan cone . . . . Routine leveling to the S end of Matupit Island on 16 March showed no significant change compared to measurements made on 24 February."
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: L. Sipison and C. McKee, RVO.