Spasmodic tremor and temporally coincident shallow earthquakes of amplitude <= 0.7 µm were recorded on 30-31 December at several seismic stations in the vicinity of Kliuchevskoi and Bezymianny volcanoes. A lack of seismic stations hampered precise estimates of location and the resolution of which volcano was closer to the focal points. The observed pattern of seismic activity was judged more characteristic of Kliuchevskoi. In addition, on 3 January another swarm of shallow earthquakes accompanied by spasmodic tremor was recorded near Kliuchevskoi's NE slope. Scientists use a color code to characterize the level of concern about volcanic activity. To indicate increased concern at Kliuchevskoi the color was shifted from green to yellow on 4 January indicating restlessness. For the week ending on 12 January, tremor at Kliuchevskoi prevailed for 7-9 hours a day, and shallow earthquakes took place 2-4 times/day.

Geological Summary. Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

Information Contacts: V. Kirianov, IVGG.