During mid-September 2001 through at least mid-June 2002 activity at Kliuchevskoi was characterized by brief periods of increased seismicity and minor surface activity. Earthquakes up to M 3 occurred (table 3) along with weak spasmodic tremor with a maximum amplitude up to 1.5 x 10^-6 m/s (table 4). Gas-and-steam plumes often accompanied the increased seismicity and were visible reaching up to 2.0 km above the crater (table 5).

Table 3. Seismicity at Kliuchevskoi during mid-September 2001 through mid-June 2002. Courtesy KVERT.

Table 4. Tremor recorded at Kliuchevskoi during mid-September through mid-June 2002. Courtesy KVERT.

Table 5. Plumes visible at Kliuchevskoi during 13 September 2001 to 20 June 2002. Plumes were visible from Klyuchi town unless noted otherwise. Heights are above the crater. Courtesy KVERT.

On 13 November a swarm of shallow M 3 earthquakes caused the Kamchatkan Volcanic Eruption Response Team (KVERT) to increase the Alert Level from Green to Yellow. According to a pilot's report, at 1315 on 19 November powerful fumarolic activity was observed. Seismicity decreased during the following days and on 23 November KVERT decreased the Color Code to Green. Seismicity remained at or near background levels with only slight increases in activity until 31 May when a series of earthquakes (up to M 2.3) was recorded in the volcano's edifice. As a result, the Color Code was increased to Yellow.

During 31 May-7 June ~20 earthquakes occurred daily at a depth of ~30 km (table 3). Overflight observations on 9 June indicated fresh ash on the volcano's slopes. The deposits were not accompanied by visually or seismically detected explosions. At the end of the report period, seismicity was slightly above background with a small gas-and-steam plume visible from nearby villages.

Geological Summary. Klyuchevskoy is the highest and most active volcano on the Kamchatka Peninsula. Since its origin about 6,000 years ago, this symmetrical, basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during approximately the past 3,000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 and 3,600 m elevation. Eruptions recorded since the late 17th century have resulted in frequent changes to the morphology of the 700-m-wide summit crater. These eruptions over the past 400 years have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

Information Contacts: Olga Chubarova, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Tom Miller, Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological and Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.