GNGTS 2019 - Atti del 38° Convegno Nazionale

764 GNGTS 2019 S essione 3.3 Conclusions In this work I have presented a new coherency measure functional based on the Continuous Wavelet Transform. The new estimator was applied to compute the velocity spectra with in the framework of the velocity analysis of seismic reflection data. The synthetic and field examples demonstrate the effectiveness of the new wavelet-based functional to compute high-resolution velocity spectra when seismograms are affected by heavy attenuation, making it possible to detect low-amplitude events and to be robust against noise. Acknowledgements. Part of this work was developed within the framework of the Research Projects of the University of Pisa (PRA 2018-2019), which is gratefully acknowledged. The code used in this work was implemented in Matlab (University of Pisa Campus Licence). I also wish to thank Landmark Graphics Corporation for the use of ProMAX for seismic data processing. References Abbad, B., and Ursin B.; 2012: High-resolution bootstrapped differential semblance . Geophysics, 77, no. 3, U39– U47, DOI 0.1190/geo2011-0231.1. Daubechies I.; 1990: The wavelet transform time-frequency localization and signal analysis. IEEE Transaction on Information Theory, 36, 961-1005, DOI 10.1109/18.57199. Daubechies I.; 1992: Ten Lectures on Wavelets. Society of Industrial and Applied Mathematics, 357 pp., DOI 10.1137/1.9781611970104. Key, S. C., and Smithson S.B.; 1990: New approach to seismic-reflection event detection and velocity determination . Geophysics, 55, 1057–1069, DOI 10.1190/1.1442918. Neidell, N. S., and Taner M.T.; 1971: Semblance and other coherency measures for multichannel data . Geophysics, 36, 482–497, DOI 10.1190/1.1440186. Spagnolini, U., L. Maciotta, and Manni A.; 1993: Velocity analysis by truncated singular value decomposition . 63rd Annual International Meeting, SEG, Expanded Abstracts, 677–680. Tognarelli, A., Aleardi, M. and Mazzotti A.; 2016: Estimation of a high resolution P-wave velocity model of the seabed layers by means of global and a gradient-based FWI . Second Applied Shallow Marine Geophysics Conference. Extended Abstract, DOI 10.3997/2214-4609.20160214. Tognarelli, A., Stucchi, E., Ravasio, A., and Mazzotti A.; 2013: High-resolution coherency functionals for velocity analysis: An application for subbasalt seismic exploration . Geophysics, 78 (5), U53-U63, DOI 10.1190/GEO2012- 0544.1 Fig. 3 - Left: real CMP gather. From left to right: velocity spectra computed by the Semblance, by the Complex Matched Semblance and by the Wavelet-based functional (only the scales corresponding to 20, 15, 10 and 5-Hz are illustrated).