Hybrid approach for travel time seismic tomography in elliptical anysotropic media

Hybrid approach for seismic travel time tomography is proposed in the case of elliptical anisotropic media. A sequential scheme is presented that combines Simulating Annealing with Linearized Least Squares inversion: at first, Simulated Annealing is implemented to obtain a velocity model that can be used as initial guess for successive Linearized Least Square inversion; in the meantime Linear Traveltime Interpolation is diffusely used to trace raypaths and calculate traveltimes. The procedure was tested both for a synthetic model and a field study. Since the field study come from a previous study, uniquely solved by Linearized Least Squares inversion without suggestions for initial guess of the velocity model, we were interested in evaluating upgrades from hybrid approach compared with solutions coming from a single technique. We found hybrid approach able to individuate a better velocity model with respect to a ”single technique” approach but, as the improvement was slight despite of the big amount of computation time needed by simulated annealing, we had also an indirect validation of the previous results of the field study.