RABAUL UPDATE 9/26/94 1500 PDT
The following is taken from a telephone conversation between scientists at CVO
and Chris McKee and Rod Stewart of the Rabaul Volcano Observatory (RVO).
Vulcan is no longer erupting. No portion of Vulcan has
collapsed. Tavurvur is still erupting an ash plume. There is an
ashy haze over Rabaul town. Seismicity is much decreased--
now at about the limit of RSAM (Real Time Seismic Amplitude) detection.
RVO no longer has the ability to locate earthquakes. Three
seismic stations remain in operation. The other stations have
been incapacitated by tsunamis, vandalism, or heavy ash fall.
About 40 mm of fine powdery ash has fallen at RVO. The
airport received about 0.5 m of ash, and the airfall thickens
rapidly towards Matupit Island.
At 0300 local on Sunday 9/18 a magnitude 5.1 earthquake
occurred beneath the harbor. An aftershock sequence from this
event merged into an intensifying swarm of high-frequency (A-
type) earthquakes. Peak intensity of this swarm occurred around
midnight Sunday with about 2 felt events per minute. The
earthquake swarm tapered off slightly toward moming. By 0600
Monday, the eruption had begun. Thus only 27 hours of unusual
seismicity preceded the eruption.
Inspection of seismograms since the onset of the eruption
revealed that several L-P events had occuffed in the 12 hours
prior to the magnitude 5.1 earthquake.
CVO/VDAP will send three volcanologists, a seismic system
consisting of telemetered seismic stations and a PC-based data-
acquisition and analysis system, several telemetered tiltmeters
and other deformation monitoring instrumentation on Wednesday