Examples of the first analyses of broadband GEOSCOPE data at station SSB (France) detailed study of the deep mantle discontinuities. Analysis of the P-coda of earthquakes using specific methods suggests the existence of P to S conversions at 670 km depth beneath SSB for earthquakes with northern to eastern azimuths; a comparison with results from the NARS and Grafenberg arrays indicate that the 670 km heterogeneous or horizontally discontinuous. A frequency analysis reveals that the relevant discontinuity is not very sharp (~20 to 70 km thick). Besides, a sharp (<5 km thick) discontinuity at 900 km depth is observed beneath the Mid-Atlantic Ridge from P reflections, giving PP precursors, for the strong March 1985 Chilean earthquake, but no 670 km discontinuity seems to be present beneath the Ridge. |