EREBUS STUDIES AND IMESS (K4) - R.R. Dibble.

1982 was our best year so far in terms of data collected. The summit induction loop, which was broken by a bomb, was repaired by W.I. McIntosh, R. Mason and party plus Helo on 25 January 1982, and recording tapes up to 16 February were dispatched to Japan before the last flight out. All sensors, transmitters, receivers and recorders were fully operational until late May when the loop stopped working. Abbott transmitter died in early June. Early on 21 July, Summit, Hooper and Bomb began recording a swarm of earthquakes. On 22 July they were occurring every minute or so, and died away during the next 3 days. There were vague reports of a glow in the sky on or about 21 July at this time.

By the 3rd of August, the Summit, Bomb and Abbott transmissions had all become very weak and intermittent, but Hooper and Terror were still O.K. Terror dropped out by 11 August, and on 17 August, Ross Mason wrote that all the equipment had stopped working. Fortunately, he did not turn the receiver/recorder off, because by 23 August there was enough sky light reaching the solar cells to revive Hooper and Abbott. Bomb was intermittent until about 24 September, but Summit stayed dead because it did not have a solar cell.

When the Japanese party (Kaminuma, Ueki and Koyama) arrived at McMurdo in November they examined the recordings from 23 August onward. Between 13 and 25 September, earthquakes were recorded at a rate of 92/day (average). From 25 to 30 September it was 117/day and then jumped to 184/day until 2 October, after which it was again 117/day until 7 October.

Suddenly at 0248 UT on 8 October a swarm of earthquakes began. In the next 24 hours at least 640 earthquakes occurred, initially separate earthquakes and with sharp P and S phases at Abbott (the closest station); S-P 2.8s), but after a few minutes continuous tremor began, and clear P and S phases were not often discernible. Five of the best recorded earthquakes in the first 7 minutes were grouped near Fang Ridge under the Fang Glacier.

Within a day after the swarm, earthquakes were back to 106/day, and slowly declined to 74/day by 9 November, the date up to which the recordings have been replayed.

Observations were made of Erebus crater activity in the 13 day period over which equipment in the summit area was being repaired, and are presented in Table 1.

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