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Report on Vailulu'u (United States) — February 1995

Bulletin of the Global Volcanism Network, vol. 20, no. 2 (February 1995)
Managing Editor: Richard Wunderman.

Vailulu'u (United States) Seismicity ends after 145 events detected by T-waves

Please cite this report as:

Global Volcanism Program, 1995. Report on Vailulu'u (United States) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 20:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199502-244000.

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United States

14.215°S, 169.058°W; summit elev. -592 m

All times are local (unless otherwise noted)

The RSP stations in Tahiti registered acoustic T-waves (tertiary waves traveling through the ocean) beginning on 8 January. This seismic swarm ended after 9 small and 5 stronger events in early February. The total number of recorded events during this swarm was 100 small and 45 larger events. Twelve of the larger events in January (M 4.2-4.8), detected and located by the world-wide seismic network, showed that the swarm was spread ~130 km along a NW-SE trend,~50 km NE of Ta'u Island (see figure 1) in the E Samoa Islands.

Geologic Background. Vailulu'u, a massive basaltic seamount not discovered until 1975, rises 4,200 m from the sea floor to a depth of 590 m about one-third of the way between Ta'u and Rose islands at the E end of the American Samoas. It is considered to mark the current location of the Samoan hotspot. The summit contains a 2-km-wide, 400-m-deep oval-shaped caldera. Two principal rift zones extend E and W from the summit, parallel to the trend of the hotspot. A third less prominent rift extends SE of the summit. The rift zones and escarpments produced by mass wasting phenomena give the seamount a star-shaped pattern. On 10 July 1973, explosions were recorded by SOFAR (hydrophone records of underwater acoustic signals). An earthquake swarm in 1995 may have been related to an eruption. Turbid water above the summit shows evidence of ongoing hydrothermal plume activity.

Information Contacts: F. Schindele, LDG, Tahiti; NEIC.