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Immediate Report of Victoria University Of Wellington Antarctic Expedition 1987-88: VUWAE 32

Seismic and Video Telemetry Studies of Mount Erebus, Antarctica. — Abstract

page 39

Seismic and Video Telemetry Studies of Mount Erebus, Antarctica.

Abstract

During the period of 16th December 1986 to 7th January 1987, 65 eruptions of Mt Erebus, Antarctica were recorded on videotape by a television camera mounted on the crater rim. The associated earthquakes were recorded on a net of nine seismometers and two infrasonic microphones. Timing on seismic and video records enabled reading to 0.04 s but due to their emergent nature, onset times were rarely this accurate. Plotting seismic arrival times from stacked eruptions against distance from the crater showed the seismic intercept time to be 1.48±0.05 s later than the time of visible explosion, and gave a surprisingly high apparent seismic velocity of 4.0±0.1 km/s. These values suggest that the source of the seismic waves is the visible explosion rather than that the seismic waves trigger the explosion. 60 of the recorded eruptions occurred in and around the lava lake, throwing out bombs and being accompanied by earthquakes. The other five took the form of ash jets, from vents near the lava lake, and were weakly seismic or aseismic. Time in night measurements for bombs gave ejection velocities ranging from 5 to 75 m/s and a maximum thrown height of 300 m above the lava lake.