Seismicity and source parameters of earthquakes in the region of the large tolbachik fissure eruption

Abstract

This study discusses the focal mechanisms of 61 earthquakes and dynamic parameters of 97 earthquakes (mi, ≥ 2.0 and focal depths 0–20 km) occurring in the region of the large Tolbachik fissure eruption in 1975–1978. Variations of these parameters during the different eruptive stages are examined. Three stages can be distinguished: 1) June 27–July 2, 1975 (from the beginning of the seismic preparation to the large earthquakes of July 2nd withM=5.0); 2) July 2nd-July 6th, 1975 (before the onset of eruption); 3) From July 6th, 1975 to the end of 1976 (during the eruption).