Investigation of deep slab structure using long-period S waves

Travel times and amplitudes of long-period SH, ScSH, sSH; and sScSH phases from several deep focus earthquakes in the northwest Pacific are analyzed for evidence of lithospheric slab penetration into the lower mantle. Inclusion of amplitude observations in the analysis provides constraints on lateral velocity gradients present in the deep slabs which are not resolvable using travel times alone. The observations support shorter and/or broader slab models than those previously hypothesized: models which can probably be reconciled with P wave data. -from Authors