Conclusions

The Soviet program of deep seismic sounding is designed to explore the vast expanses of that country with underground nuclear explosions augmented by ultra-deep drill holes. The fact that the program has been operating since 1971 and shows every promise of continuing is testimony to its successes and usefulness to Soviet objectives. Such a notable program has been possible despite an apparent dearth of digital recording equipment and advanced analytical tools. The use of large seismic sources has allowed elucidation of crustal detail and mantle structure down to a depth of 200 km. Analysis of data has revealed gross inhomogeneities in the mantle un-derlying the Soviet Union. Comparable structures have not been described on other continents.