KLYUCHEVSKOI VOLCANO 56o11' N, 160o47' E May 19, 1993 Via GVN In July 1992, during observations from the aircraft over Kliuchevskoi, it has been found by S.A. Fedotov that almost all the cone, which was formed during 1984-1990, has subsided. The aerophotosurvey made on 4 April 1993 confirmed this and allowed more precise estimation of the the scales of the current event. In April 1993, the newly-formed crater at the summit of the volcano had a diameter of 500 m and a depth of 200 m. Failures of such a scale are quite seldom events at Kliuchevskoi. The last case like this took place during 1962-1968. A small new volcanic cone was found on the floor of the formed crater. A slight lava fountaining was observed from its vent. In the middle of March 1993, after a short period of repose, the activity of the volcano increased. Explosions occurred in the central crater, the ash-gas cloud rose 1-2 km above the summit. On 15 March, volcanic tremor appeared, from 15 April its amplitude started to increase, reaching its maximum value of 2.4 microns (vertical component 13 km) in the first decade of May. At the present time the amplitude of tremor is decreased. Tremor at Kliuchevskoi is noticed very often and is related, as usual, to the eruptive activity of the summit crater and to a lesser degree to flank eruptions. The amplitude of tremor is largely dependent on the style of volcanic activity: amplitude smaller than 0.5 microns is associated with steam-gas emission; 0.5-3 microns with Vulcanian explosions; more than 3 microns with Strombolian explosions or lava spouting. We suppose that the appearing and increase in volcanic tremor indicate that the volcanic eruption is still slight and the pressure in the magma feeding system of the volcano is increasing. Information contacts: V.V. Ivanov and V.N. Dvigalo. Institute of Volcanology, Petropavlovsk-Kamchatskii, 683006, Russia.