HR: 13:40h
AN: T53D-01    [Abstracts]
TI: The three dimensional Vs-wavespeed and lithospheric structure of the East Asian mantle
AU: * Priestley, K
EM: keith@esc.cam.ac.uk
AF: Bullard Laboratories, Dept. of Earth Sciences, University of Cambridge, Madingley Rise, Madingley Road, Cambridge, CB3 0EZ United Kingdom
AU: Mckenzie, D
EM: mckenzie@esc.cam.ac.uk
AF: Bullard Laboratories, Dept. of Earth Sciences, University of Cambridge, Madingley Rise, Madingley Road, Cambridge, CB3 0EZ United Kingdom
AU: Debayle, E
EM: Eric.Debayle@eost.u-strasbg.fr
AF: Ecole et Observatiore des Sciences de la Terre, Universite Louis Pasteur, 5 rue René Descartes, Strasbourg, 67084 France
AU: Pilidou, S
EM: s_pilidou@yahoo.co.uk
AF: Bullard Laboratories, Dept. of Earth Sciences, University of Cambridge, Madingley Rise, Madingley Road, Cambridge, CB3 0EZ United Kingdom
AB: We present a new 3D S_v-wavespeed and azimuthal anisotropy model for the upper mantle of eastern Asia constrained by the analysis of more than 17,000 vertical component, short path (<6000~km) Rayleigh wave multi-mode seismograms. The dense path coverage, wide azimuthal distribution and rich higher mode content of the data set allow us to build an upper mantle model for Asia with a horizontal resolution of a few hundred kilometers extending to ~400~km depth. At 75-100~km depth there is approximately ±9% wavespeed perturbation from the ``smoothed PREM'' reference model used in our analysis, and the pattern of azimuthal anisotropy is complex. Both the amplitude of the S_v-wavespeed heterogeneity, and the complexity and amplitude of the azimuthal anisotropy decrease with depth. Above ~200~km depth the upper mantle structure of the model correlates with surface geology and tectonics; below ~200~km depth the structures primarily reflect the advection of material in the upper mantle. Since Vs-wavespeed is principally controlled by temperature, rather than by composition, Vs(z) can be used to calculate the temperature T(z), and hence map the lithospheric thickness. We combine the thermal model of McKenzie et al (2005) for the Pacific lithosphere with a S_v-wavespeed model for the Pacific obtained from surface wave tomography, to obtain an empirical relation for Vs(T). The resulting expression is tested by calculating continental geotherms from Vs(z) obtained from surface wave tomography, and comparing these with geotherms calculated from the mineralogy of kimberlite nodules. The agreement is excellent, especially at higher temperature. We use this empirical relationship to produce a contour map of the lithospheric thickness of eastern Asia from the surface wave tomography. This shows an extensive region of thick lithosphere beneath the Siberian Platform and the West Siberian Basin, and extending to the European Platform, forming the stable Eurasian craton or core. The eastern portion of the Eurasian craton has controlled the geometry of continental deformation and the distribution of kimberlites in Eastern Asia.
DE: 8103 Continental cratons
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8159 Rheology: crust and lithosphere (8031)
DE: 8180 Tomography (6982, 7270)
SC: Tectonophysics [T]
MN: Fall Meeting 2005