Now about 700 volcanoes are believed to be active in the world. In this paper, both theoretical and experimental grounds of the monitoring system of living volcanoes with the use of powerful vibroseismic sources are considered. A method to calculate Green's function for inhomogeneous models of media with employment of the reciprocity principle was developed for the numerical modeling of arbitrary structures, in particular, magma chambers. A medium is assumed to consist of arbitrary blocks. A certain part of the medium can be a layered pack with an arbitrary number of layers. The thickness of layers and the velocity parameters of media can be arbitrary quantities in both the layered pack and in the block medium. It should be noted that the calculation of Green's function allows simultaneous calculation of the wave fields for an arbitrary number of sources and receivers. This is also important for problems of the 3D (areal) seismic prospecting and for solving inverse problems of geophysics by using optimization methods.