Shear velocity structure of central Eurasia from inversion of surface wavevelocities

We present a shear velocity model of the crust and upper mantle beneath cen tral Eurasia by simultaneous inversion of broadband group and phase velocit y maps of fundamental-mode Love and Rayleigh waves. The model is parameteri zed in terms of velocity depth profiles on a discrete 2 degrees x 2 degrees grid. The model is isotropic for the crust and for the upper mantle below 220 km but, to fit simultaneously long period Love and Rayleigh waves, the model is transversely isotropic in the uppermost mantle. from the Moho disc ontinuity to 220 km depth. We have used newly available a priori models for the crust and sedimentary cover as starting models for the inversion. Ther efore, the crustal part of the estimated model shows good correlation with known surface features such as sedimentary basins and mountain ranges. The velocity anomalies in the upper mantle are related to differences between t ectonic and stable regions. Old, stable regions such as the East European, Siberian, and Indian cratons are characterized by high upper-mantle shear v elocities. Other large high velocity anomalies occur beneath the Persian Gu lf and the Tarim block. Slow shear velocity anomalies are related to region s of current extension (Red Sea and Andaman ridges) and are also found bene ath the Tibetan and Turkish-Iranian Plateaus, structures originated by cont inent-continent collision. A large low velocity anomaly beneath western Mon golia corresponds to the location of a hypothesized mantle plume. A clear l ow velocity zone in nu (SH) between Moho and 220 km exists across most of E urasia, but is absent for nu (SV). The character and magnitude of anisotrop y in the model is on average similar to PREM, with the most prominent aniso tropic region occurring beneath the Tibetan Plateau. (C) 2001 Elsevier Scie nce B.V, All rights reserved.