GNGTS 2017 - 36° Convegno Nazionale

548 GNGTS 2017 S essione 3.1 problem, and applicable at low seismic frequencies where the S/N ratio could be low. Starting from a velocity model obtained by a previous global optimization procedure based on genetic algorithms we estimated, by means of a gradient-based method, a final model whose quality is assessed by the good correspondence between the predicted and the observed data and by the improvements of the horizontal alignment of the events in the CIGs. Acknowledgements The authors wish to thank Eni for its continued support in the research. The seismic data processing was carried out using the Promax software of Landmark Graphics Corporation that is gratefully acknowledged. References Beydoun, W. B. and Tarantola A.; 1988: First Born and Rytov approximations: Modeling and inversion conditions in a canonical example . The Journal of the Acoustical Society of America, 83, 1045–1055. doi: 10 .1121/1.396537. Chaljub E., Komatitsch D., Capdeville Y., Vilotte J.P., Valette B., Festa G.; 2007: Spectral-element analysis in seismology. In: Advances in Geophysics, 48, 365-419. Fichtner, A.; 2010: Full Seismic Waveform Modelling and Inversion . Berlin: Springer-Verlag. Galuzzi B., Stucchi E. and Zampieri E.; 2015: Optimal parameters for finite difference modeling of 2D seismic wave equation . Atti del 34-esimo Convegno del Gruppo Nazionale di Geofisica della Terra Solida, 153-159. Mazzotti A., Bienati N., Stucchi E., Tognarelli A., Aleardi M. and Sajeva A.; 2016: Two-grid genetic algorithm full- wave form inversion . The Leading Edge, 35, 1068-1075. doi: 10.1190/tle35121068.1 Mozco P., Kristek J., Gàlis M. 2007: The finite-difference and the finite-element modelling of seismic wave propagation and earthquake motion . Acta Physica Slovaca, 177-406 Nocedal J. and Wright S., 2006: Numerical Optimization . Springer-Verlag. NewYork. doi: 10.1007/978-0-387-40065- 5 Plessix R.; 2006: A review of the adjoint-state method for computing the gradient of a functional with geophysical applcations . Geophysical Journal International, 167, 495-503. doi: 10.1111/j.1365-246X.2006.02978.x Sajeva A., Aleardi M., Stucchi E., Bienati N. and Mazzotti A.; 2016: Estimation of acoustic macro models using a genetic full-waveform inversion: Applications to the Marmousi model . Geophysics, 81, 173-184. doi: 10.1190/ geo2015-0198.1 Tarantola, A. ;1986: A strategy for nonlinear elastic inversion of seismic reflection data . Geophysics, 51, 1893-1903 Tognarelli A., Stucchi E., Bienati N., SajevaA., Aleardi M. and Mazzotti A.; 2015: Two-grid Stochastic Full Waveform Inversion of 2D Marine Seismic Data . 77 th EAGE Conference and Exhibition, 81 (4), 173-184 Tromp, J., Tape C., Liu Q.; 2005: Seismic tomography, adjoint methods, time reversal, and banana-doughnut kernels . Geophysical Journal International, 160, 195-216. Virieux, J. and Operto, S.; 2009: An overview of full waveform inversion in exploration geophysics . Geophysics , 127-152. Wolfe P.; 1969: Convergence Conditions for Ascent Methods . SIAM Review (Society for Industrial and Applied Mathematics), 11, 226-235. ANALYSIS OF GLACIMARINE SEDIMENTS BY TRAVEL TIME REFLECTION TOMOGRAPHY IN THE EASTERN ROSS SEA (ANTARCTICA) A. Geniram 1 , G. Böhm 2 , L. De Santis 2 , A. Camerlenghi 2 1 Università degli Studi di Trieste, Italy 2 Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS, Italy Introduction. This work presents the results of a study whose aim is to investigate the nature of acoustic facies and of their seismic interfaces, from geophysical analysis in order to reconstruct P waves velocity of glacial sediments across the drill site DSDP270 (Hayes and Frakes, 1975), in the Eastern Ross Sea (Antarctica). The applied technique, combined with lithological information from the drill site, allows to identify petrophisical properties (e.g. compaction, fluid content) related to the depositional process, that originated the different acoustic facies. The correlation of seismic facies in the