It was common opinion, till ten years ago, that in mantle should exist an only guide channel of seismic energy: the asthenosphere. The study of deep focus earthquakes (beyond the 600 kms) made supposing the existence of surfaces (or layers) able to guide some shear seismic energy, associated with waves of channel wave type. Several large trains of waves, after the SS-waves, awaited a physical explanation. Ibrahim and Nuttli (1967) and Anderson and Jordan (1969, 1973) proved the existence of low velocity S-waves layers about 400 kms and, especially, about 650 kms deep. In this work one demonstrates that the above mentioned trains of waves are channel waves guided by the low velocity S-waves layers. The weakness of the overhanging layers permits to the seismic energy to reach the earth surface, as surface waves.