Natural SciencesEarth SciencesGeophysicsSeismologyTectonicsTectonophysicsLithospheric DeformationLithospheric FlexurePropagation ModelingSeismic AttenuationSeismic Wave GenerationSeismic Wave PropagationLithosphere-mantle CouplingLong-range PropagationPlanetary Lithosphere DynamicsRadiated Seismic EnergySeismic Energy DissipationSeismic Energy SpectraSeismic Wave Propagation In The Mantle
Observations of seismic arrivals from the lower lithosphere in France revealed a low mean velocity of observed first arrivals of about 8.1 km/s between 150 and more than 1000 km distance and several high velocity phases with apparent velocities between about 8.2 and 8.6 km/s.Each one of these high velocity phases is only observed over a range of about 100 or 200 km.The possibility of interpreting these phenomena in terms of fine structure of the lower lithosphere is investigated.The resulting model consists of alternating high and low velocity layers.No first order discontinuities seem to exist between these layers.A reliable quantitative estimate of the thickness of these high and low velocity zones can only be obtained by a joint travel time and amplitude study.