GNGTS 2017 - 36° Convegno Nazionale

688 GNGTS 2017 S essione 3.3 of the inverted values, as standard deviation of the posterior model normalized to the standard deviation of the prior model (Fig. 2 right). We tested many hybrid inversion sequences on the tutorial model: a very interesting approach is a first phase of SA, in order to place the current candidate point in the region of the global minimum, followed by a BLI, that pushes in few steps the candidate to the global solution. In conclusion, complex inverse problems can be tackled with hybrid procedures, involving global and Bayesian methods. The whole process has to be preferably supervised. In this framework, the analysis tools presented here are very effective in highlighting “in real time” the most important information about the inversion status, the sensitivity of the observed data with respect to the model parameters, and the accuracy of the solution. References Bosisio, A., Drufuca, G., Rovetta, D.; The concept of distance in global optimization applied to non-linear inverse problems, Inverse problems in science & engineering, 22, 683-706, 2014. Constable S.; Ten years of marine CSEM for hydrocarbon exploration. Geophysics, 75, A67–75A81, 2010. Constable, S., and C. J. Weiss, Mapping thin resistors and hydrocarbons with marine EM methods: Insights from 1D modeling: Geophysics, 71, 2, G43–G51, 2006. Corana, A., Marchesi, M., Martini, C., Ridella, S.; Minimizing Multimodal Functions of Continuous Variables with the Simulated Annealing Algorithm; ACM Transactions on Mathematical Software, 13,262-280, 1987. Hastings,W.K., Monte Carlo sampling methods using Markov chains and their applications , Biometrikam, 57, 97- 109, 1970 Kirkpatrick, S., Gelatt, C.D., Vecchi, M.P.; Optimization by Simulated Annealing, Science, 1983. Metropolis N., Rosenbluth A.W., Rosenbluth M.N., Teller A.H., and Teller E., Equation of State Calculations by Fast Computing Machines, J.Chem.Phys., 1, 1087-1092, 1953. Vandone, V., Chiappa, F., Bernasconi G., Csem Sharp and Stable Imaging by Means of Probabilistic Inversion, Contractions-By-Bisections Line Search and Full Covariance Operator, Atti GNGTS, 2014. Fig. 3 - Simulated Annealing inversion evolution. Imaging of sharp lateral variations in the subsoil: a numerical comparison of surface-wave based methods C. Colombero 1 , E.I. Cojocariu 2 , C. Comina 1 , L.V. Socco 2 1 Dipartimento di Scienze della Terra, Università degli Studi di Torino, Italy 2 Dipartimento di Ingegneria dell’Ambiente, del Territorio e delle Infrastrutture, Politecnico di Torino, Italy Introduction. Near-surface heterogeneities including fractures, faults, cavities, buried low- velocity bodies or slopes with strong lateral contrasts in physical and mechanical properties, are a common target of investigation in surface seismic surveys. Dealing with such abrupt,