Simulated annealing in 3-D seismic modelling and elastic structure of the Mediterranean basin

3-D elastic structures images of the Mediterranean basin are obtained by so lving a tomographic problem by means of a simulated annealing algorithm. Th e database consists of local Rayleigh wave group velocities determined for the fundamental mode in the 10-90s period range. These local velocities wer e obtained from surface wavetrains recorded at very broad band stations of MEDNET network. From a methodological point of view, the characteristics of the annealing algorithm and the amount of time required for computation su ggest the implementation of parallel computational procedures to shorten th e computational time. According to the thermodynamic analogies used in the annealing algorithm, we propose an alternative procedure to estimate uncert ainties and correlations for variables defining the elastic model (shear ve locities and layer thicknesses) without necessity of computing partial deri vatives. From an applied point of view, the 3-D elastic model obtained show s, as main results, relevant differences for the eastern and western parts of the Mediterranean basin, specially down to 60 km. The changes in the pos ition of the top and bottom asthenosphere surfaces can also be followed thr oughout the Mediterranean basin; remarkably, these changes are in agreement with some tectonic features. Keywords: Mediterranean basin, Rayleigh waves , tomography, simulated annealing. (C) 1999 Elsevier Science Ltd. All right s reserved.