Report on Ulawun (Papua New Guinea) — December 1983

Scientific Event Alert Network Bulletin, vol. 8, no. 12 (December 1983)
Managing Editor: Lindsay McClelland.

Ulawun (Papua New Guinea) Seismicity increases after M 6.4, 6.5 earthquakes

Please cite this report as:

Global Volcanism Program, 1983. Report on Ulawun (Papua New Guinea). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 8:12. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.SEAN198312-252120.

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Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


"Volcano-seismic activity continued at a low level throughout most of December but increased suddenly again with the appearance of continuous harmonic tremor at 0200 on 24 December, less than 2 days after two strong regional earthquakes (ML 6.4 and 6.5, MM IV-V) about 150 km ESE of Ulawun at 0932 and 1102 on 22 December.

"The first period of harmonic tremor, which was low in amplitude, lasted less than 2 hours. It was followed by three days (23-26 December) of high seismic activity consisting of further periods of low-amplitude, continuous and discontinuous harmonic tremor and numerous larger-than-normal B-type volcanic events. No changes to the normal white vapour emission were observed during the seismic crisis. Disturbances consisting of loud bangs and the production of vapour rings were observed from Ulamona Catholic Mission on 15-16 and 20-21 December, but were not accompanied by any events on the seismic records."

Geologic Background. The symmetrical basaltic-to-andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea's most frequently active. Ulawun volcano, also known as the Father, rises above the north coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1000 m of the 2334-m-high Ulawun volcano is unvegetated. A prominent E-W-trending escarpment on the south may be the result of large-scale slumping. Satellitic cones occupy the NW and eastern flanks. A steep-walled valley cuts the NW side of Ulawun volcano, and a flank lava-flow complex lies to the south of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater.

Information Contacts: P. Lowenstein, RVO.