Report on Rabaul (Papua New Guinea) — February 1990
Bulletin of the Global Volcanism Network, vol. 15, no. 2 (February 1990)
Managing Editor: Lindsay McClelland.
Rabaul (Papua New Guinea) Seismicity continues to decline; no significant deformation
Please cite this report as:
Global Volcanism Program, 1990. Report on Rabaul (Papua New Guinea) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 15:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199002-252140
Papua New Guinea
4.271°S, 152.203°E; summit elev. 688 m
All times are local (unless otherwise noted)
"A further decline in activity was evident in February. The total number of caldera earthquakes recorded in February was 161. Daily earthquake totals ranged between 0 and 17. The earthquakes occurred on the NE and NW-SW parts of the caldera seismic zone. The strongest was an ML 3.1 event from the SW part of the zone on the 28th. Levelling measurements on the Rabaul Town-Matupit Island line carried out on 20 February indicated little or no change since the previous measurements (9 January)."
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 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.