GNGTS 2015 - Atti del 34° Convegno Nazionale

GNGTS 2015 S essione 3.3 159 derivatives. Therefore an optimal trade-off between these two parameters is required in order to reduce the approximation error. This approximation error can also be analysed in terms of the grid dispersion relation and therefore in terms of the ratio between theminimumvelocity cmin in themodel and themaximum frequency f max of the wavelet. If the ratio is low, it is necessary to use a low spatial step size and a medium order of spatial derivative approximation (for instance: dx =9 m and ord s =6,8). If the ratio is high, it is possible to use a greater spatial step size, but with a higher order of spatial approximation (for instance: dx =27 m and ord s =22,24). As a final consideration, if there are combinations of these two parameters that cause comparable errors, it is convenient to use the one with the greater space step size to reduce the execution time, especially in application such as the Full Waveform Inversion where a large number of forward modelling may be needed. References Williamson, P. R., & Pratt, R. G. (1995). A critical review of acustic wave modeling procedures in 2.5D dimensions. Geophysics , 60 , 591-595. Virieux, J., & Operto, S. (2009). An overview of full waveform inversion in exploration geophysics. Geophysics , 127-152. Aki, K., & Richards, P. G. (2002). Quantitative Seismology (2nd ed.). University Science Books. Alford, R. M., Kelly, K. R., & Boore, D. M. (1974). Accuracy of finite difference modeling of the acoustic wave equation. Geophysics , 39 (6), 834-842. Bleinstein, N. (1986). Two-and-One-Half Dimensional in-Plane Wave Propagation. Geophysical Prospecting , 34 , 686-703. Bourgeois, A., Bourget, M., Lailly, P., Ricarte, P., & Versteeg, R. (1991). Marmousi, model and data. European Association of Exploration Geophysicists. Cerjan, A., Kosloff, D., Kosloff, R., & Reshef, M. (1985). A non reflecting boundary condition for discrete acoustic and elastic wave equations. Geophysics , 50 , 705-708. Courant, R., Friedrichs, K., & Lewy, H. (1967, March). On the partial difference equations of mathematical physics. IBM Journal , 215-234. Cohen, G. (2002). Higher-order Numerical Methods for Transient ave Equations. Berlin: Springer-Verlag. Fichner, A. (2010). Full Seismic aveform Modelling and Inversion. Berlin: Springer-Verlag. Liner, C. L. (1991). Theory of a 2.5-D acoustic wave equation for constant density media. Geophysics , 56 (12), 2114-2117. Sajeva, A., Aleardi, M., Galuzzi, B. G., Mazzotti, A., & Stucchi, E. M. (2014). Comparison of stochastic optimization methods on analytic objective function and on 1D elastic fwi. European Association of Geoscientis and Engineers Conference and Exhibition , (pp. 1893-1903). Amsterdam. Song, Z., & Williamson, P. R. (1995). Frequency-domain acoustic wave modelling and inversion of crosshole data; Part 1, 2.5-D modelling method. Geophysics , 60 (3), 784-795. Tarantola, A. (1986). A strategy for nonlinear elastic inversion of seismic reflection data. Geophysics , 51 , 1893- 1903. Application of the Reconfigurability of the Integration Time in Stepped Frequency GPR Systems: First examples in the field R. Persico 1 , D. Dei 2 , F. Parrini 2 , L. Matera 1 , S. D’Amico 3 , A. Micallef 3 , P. Galea 3 1 Institute for Archaeological and Monumental Heritage IBAM-CNR, Lecce, Italy 2 Florence Engineering s.r.l., Florence, Italy 3 University of Malta, Msida, Malta Introduction. Ground Penetrating Radar (GPR) is the tool that allows the best available resolution within the non-invasive subsurface geophysical techniques, as well known (Daniels, 2004; Jol, 2009; Persico 2014). In particular, possibly integrated with other geophysical techniques (Matera et al ., 2015), a GPR can provide information of geological, cultural, and structural interest (Ranieri et al ., 2015; Sambuelli et al ., 2014; Castaldo et al . 2009; Masini et