PECULIARITIES OF SURFACE-WAVE PROPAGATION ACROSS CENTRAL EURASIA

The recent installation of six broadband digital IRIS/IDA seismic stations in the USSR has provided new opportunities for studying surface-wave propagation across Eurasia. Group velocities of fundamental Rayleigh and Love modes between epicenters and these stations were determined for 35 events that occurred since April 1989 to the middle of July 1990 near Eurasia. Differential phase velocities were found for the same arrivals along paths between several pairs of stations. Group and phase velocities were obtained in the period range from 15 to 300 sec. Frequency-time polarization analysis was used for studying polarization properties of surface waves. In some cases, significant anomalies in the particle motion for periods up to 100 sec were observed. They are attributed to surface-wave refraction and scattering due to lateral inhomogeneities at the boundaries and inside the Eurasia continent.