Studying magma chambers beneath active volcanoes using geophysical methods is a complex but exciting task that attracts the attention of many specialists. A review by Lee [2007] gives several examples of successful application of seismic tomography tools in studying magma chambers beneath different volcanoes. More recent studies have revealed rather clear images of magma chambers beneath the Toba caldera [Koulakov et al.,2009a], Merapi volcano [Koulakov et al.,2009b], and other areas.