Attenuation of Rayleigh waves across the volcanic area of the Massif Central,France |
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Authors: | Annie Souriau Antoni M. Correig Marc Souriau |
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Affiliation: | 2. Departamento de Fisica de la Tierra y del Cormos, Universidad de Barcelona, Diagonal 645, Barcelona 28 Spain;3. Groupe de Recherches de Géodésie Spatiale, Centre National d''Etudes Spatiales, 18 Av. Edouard Belin, 31055 Toulouse Cedex France |
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Abstract: | Rayleigh wave attenuation is investigated for periods ranging from 20 to 90 s, along a 450 km-long profile following the Oligocene tensile zone of the French Massif Central. A model is deduced by inversion, assuming that the S-wave intrinsic quality factor Qβ is frequency-independent, and yields a mean value Qβ = 43 ± 10 for the first 100 km in the upper mantle. This value, far lower than the mean value obtained in Eurasia, is close to those obtained in other recent tensile areas, e.g., the western United States or mid-oceanic ridges.A velocity-depth model for S-waves, deduced in a previous study from surface-wave propagation, has been corrected for the attenuation effect. We find a discrepancy between the corrected S-model and P-wave residuals in the same area, implying that Qβ must be frequency-dependent. This can be a clue for partial melting in the upper mantle beneath this region. |
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