Features of radiation of powerful vibrators on inhomogeneous soils (high-speed, flooded, permafrost) are analyzed in this chapter. It is shown that, when emitted on high-speed ground, the effective range of emission becomes narrowband and shifts to the high-frequency region. On low-speed soils, the emission spectrum is broader, and correlograms in the far zone are more permissible and have a high signal-to-noise ratio. The role of resonances in the vibrator/subsoil system in the formation of powerful multiple and half-multiple harmonics is established. The possibility of using the latter for expanding the effective frequency range of vibrator emission and obtaining correlograms in the near and far zones is shown. It is established that when summing up repeated sessions of vibrators, the resolution of correlograms increases and the signal-to-noise ratio increases.

The conditions of the performed experiments were as follows. A three-component receiver was installed in a thermostatic pavilion of the seismological station "Novosibirsk". A vibrator (force amplitude 50-100 tons) was functioning out-of-doors. The source-receiver distance was 49 100 m. Vibration sessions were performed each one-two weeks during 1.5 years. The experiments have shown that seismograms are highly reproducible when obtained under summer ground conditions (from June till October) or in winter (from January till March). The "summer" seismograms strongly differ in appearance from the "winter" ones, but the domains of the first arrivals of P waves show the presence of stable waves. These waves are virtually the same in the "summer" and "winter" seismograms. They are recommended for monitoring the stress-strained state of a medium by periodical vibrating dangerous zones of active seismicity. The high reproducibility of vibroseismic signals (under the same seasonal conditions) enables one to register wave fields on large areas by resetting receivers. This method was used to reveal fracture sites in the Baikal Rift Zone from changes in the spectrum of received vibroseismic signals.