Inversion of Rayleigh wave phase and group velocities by simulated annealing

A joint inversion of regionalized phase and group velocities of fundamental mode Rayleigh waves is performed by means of a simulated annealing scheme which makes use of some thermodynamic analogies based on the Gibbs' distrib ution. The correlations and the uncertainties on shear-wave velocities defi ning the elastic model are estimated by using a procedure based on the same thermodynamic analogies. As a relevant feature, the simulated annealing al gorithm permits reducing the usual dependence of the solution on the someti mes arbitrary starting model. A shortcoming linked to the use of this proce dure for solving an inversion problem is the necessity of a previous empiri cal determination of some parameters controlling the annealing process. Wit h this aim, a simulation of a joint inversion of synthetic surface wave dis persion data has been performed. After that, path-averaged velocity dispers ion curves corresponding to a Hercynian area of the Iberian Peninsula have been inverted to derive two possible crust and upper mantle elastic structu res. Whereas, the first structure has been deduced by considering as unknow n variables the shear velocities of the stratified Earth model, the second has been obtained also including the respective layer thicknesses. Both str uctures are compared with shear velocity and Q(beta) models derived by the stochastic inversion procedure in previous studies and from the same Raylei gh waves dataset. Finally, advantages and shortcomings of the inversion of phase and group velocity data by means of simulated annealing are discussed . (C) 2000 Elsevier Science B.V. All rights reserved.