HR: 1340h
AN: T33A-1332    [Abstracts]
TI: Continental Upper Mantle: T, Vs, Qs
AU: * Billien, M
EM: shane@usgs.gov
AF: Ecole et Observatoire de Sciences de la Terre, 5 rue Rene Descartes, Strasbourg, F-67084 France
AU: Artemieva, I M
EM: irina@eost.u-strasbg.fr
AF: US Geological Survey, 345 Middlefield Rd. MS 977, Menlo Park, CA 94025 United States
AU: Artemieva, I M
EM: irina@eost.u-strasbg.fr
AF: Ecole et Observatoire de Sciences de la Terre, 5 rue Rene Descartes, Strasbourg, F-67084 France
AU: Leveque, J
EM: jeanjacques.leveque@eost.u-strasbg.fr
AF: Ecole et Observatoire de Sciences de la Terre, 5 rue Rene Descartes, Strasbourg, F-67084 France
AU: Mooney, W D
EM: mooney@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd. MS 977, Menlo Park, CA 94025 United States
AB: Global maps of the thermal structure of the continental upper mantle at depths 50-150 km are compared with global Qs(-1) and Vs maps as determined from Rayleigh waves at periods between 40 and 150 seconds. This allows us to evaluate the relative contributions of thermal and non-thermal effects into seismic anomalies. Vs and Qs anomalies usually inversely correlate with lithospheric temperatures. However, the available dataset does not indicate that, at a global scale, seismic anomalies in the upper mantle are controlled solely by temperature variations. Continental maps have correlation coefficients of $<$0.56 between Vs and T and $<$0.47 between Qs and T. At 100 km depth, where the resolution of seismic models is the highest, seismic Vs and Qs are compared with theoretical Vs and Qs values that are calculated solely from temperature anomalies and constrained by experimental data on temperature dependences of velocity and attenuation. This comparison shows that temperature variations alone are sufficient to explain seismic Vs and Qs in $\sim$ 50% of continental regions. We hypothesize that compositional anomalies due to Fe-depletion can explain the misfit between seismic and theoretical Vs in cratonic lithosphere; partial melts and/or fluids may affect seismic parameters in regions of active tectonics.
DE: 8123 Dynamics, seismotectonics
DE: 8124 Earth's interior--composition and state (old 8105)
DE: 8125 Evolution of the Earth
DE: 8147 Planetary interiors (5430, 5724)
DE: 7218 Lithosphere and upper mantle
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting