A vibroseismic method of studying the Earth’s deep structure has been most intensively used in the last fifteen years. Much progress has been made toward the creation of powerful seismic vibrators with precise amplitude- frequency-phase characteristics as well as toward methods and instruments for measuring the wave field parameters in the near and far zones. The present method is characterized by high logical purity, which opens up fresh opportunities for the use of the vibroseismic method when solving a number of actual seismological problems such as the vibroseismic monitoring of seismic-prone zones, vibrational seismotomography, vibrational seismic zoning, etc. In the solution of these problems of practical significance is the harmonic oscillation seismics. It is theoretically shown and experimentally verified that the attainable accuracies and the noise-proof feature in the measurement of these parameters are higher than in the conventional impulse seismics. This allows vibrational sounding of the Earth at large depths (up to hundreds of kilometers) and at extended seismic traces (longer than 1.000 km).