Report on Rabaul (Papua New Guinea) — November 1988
Scientific Event Alert Network Bulletin, vol. 13, no. 11 (November 1988)
Managing Editor: Lindsay McClelland.
Rabaul (Papua New Guinea) Seismicity declines; slight inflation
Please cite this report as:
Global Volcanism Program, 1988. Report on Rabaul (Papua New Guinea) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 13:11. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198811-252140
Rabaul
Papua New Guinea
4.2459°S, 152.1937°E; summit elev. 688 m
All times are local (unless otherwise noted)
"Seismic activity continued to decrease in November with a total of 301 earthquakes. The daily number of events averaged <20 with the highest number (54 events) recorded on the l4th. Four locatable events were detected: on the E side (1) and N of (2) Greet Harbour, and on the W side of Matupit Island (1). Ground deformation rates remained low. Levelling on 3 November showed 12 mm of uplift at the S part of Matupit Island since 20 October. EDM data showed slight expansion (5 microstrain) at Greet Harbour's entrance."
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 P. Lowenstein, RVO.