TEMPORAL AND SPATIAL CHARACTERISTICS OF VOLCANIC TREMOR WAVE FIELDS

Detailed volcanic tremor studies were carried out with portable seismic stations installed both in the near and distant zones at Klyuchevskoy volcano in 1984, 1986, and 1987. It has been determined that the coherence of wave field decreases with distance to 0.5 km and does not change at greater distances. Based on coherence and phase spectra, the frequency dependence of the phase velocities has been determined. The dispersion of phase velocity points to the surface character of the wave field. The behaviour of volcanic tremor characteristics through time is stationary, which implies stability of the parameters of the volcanic tremor source. A detailed spectral study has demonstrated that when the intensity of volcanic tremor varies by a few orders of magnitude, parts of the low-frequency and high-frequency spectra change, which is likely due to the variations in source dimensions. The detailed spectral characteristics of tremor may be used for both determining the source parameters and studying the structure of the medium. © 1990.