GNGTS 2019 - Atti del 38° Convegno Nazionale

632 GNGTS 2019 S essione 3.2 waves. We notice in both images a very shallow anomaly with a thickness of about 100 m, which corresponds to unconsolidated sediments: mainly gravel, with some sand and shale. Such a shallow discontinuity fits nicely the depth location of a shallow reflector/refractor, when superimposing the tomographic estimates to the pre-stack depth migrated seismic section (Fig. 3). Particularly interesting in the deeper formation is the correlation between seismic stratigraphy, horizon dip and anomalies for both P velocity and Q factor. However, the most surprising feature is still in the near surface, as we can notice that the shallowest formation mentioned above can be actually divided into two zones at least, with a similar boundary observed both in the P velocity and in the Q factor images. While reviewing the hydrological literature about the area (e.g., Al Shahi, 2002; El-Mahmoudi, 2004, Emahdy and Mohamed, 2014), we found out that lateral variations of aquifer properties have been observed in the Al Jaww plain by water wells and other geophysical methods. Our available data cannot draw solid conclusions about a possible different geological origin of our two aquifer areas. However, a preliminary interpretation of the compressional structure in the seismic section suggests the presence of major faults with displaced blocks. Such a tectonic complexity is expected to play a role in the lithology of the shallow aquifers too. Conclusions. The joint processing and interpretation of rock properties as P velocity, Q factor and seismic reflectivity looks to be a valuable tool to characterize shallow aquifers. The calibration with existing wells, currently not available, might validate the geophysical estimation of aquifers properties in 2D and 3D. Such information may allow optimizing the fresh water catchment and its protection from pollution. References Ali M. Y., Sirat M. and Small J.; 2008: Geophysical investigation of Al Jaww plain, eastern Abu Dhabi: Implications for structure and evolution of the frontal fold belts of Oman Mountains . Geoarabia, 13 , 91. Al Shahi F. A.; 2002: Assessment of groundwater resources in selected areas of Al Ain in the UAE. Master Thesis, United Arab Emirates University. Al-Nuaimi H. S., El-Mahmoudi A. and Sherif M.; 2004; Evaluation of the Groundwater Quality at Al Jaww Plain, Al-Ain, UAE, Eighth Annual U.A.E. University Research Conference Emahdy S. I. and Mohamed M. M.; 2014: Probabilistic frequency ratio for groundwater potential mapping in Al Jaww plain, UAE . Arabian Journal of Geosciences, Springer, doi: 10.1007/s12517-014-1327-9. El-Mahmoudi A.; 2004: Geophysical and hydrogeological investigations of the Quaternary aquifer at Al Jaww Plain, Al Ain area . Fast Times, 9 , n.1, pp. 17-28. Quan Y. and Harris J.; 1997: Seismic attenuation tomography using the frequency shift method . Geophysics, 62 , pp. 895-905. Menges C. M. and Woodward D. G.; 1993; Ground Water Resources of Al Ain area, Abu Dhabi Emirate . Unpublished administrative report 93-001, National Drilling Company, Abu Dhabi, UAE, 315 p. Rossi G. and Vesnaver A.; 2001: Joint 3D traveltime inversion of P, S and converted waves . Journal of Computational Acoustics, 9 , pp. 1407-1416. Rossi G., Gei D., Böhm G., Madrussani G. and Carcione J.; 2007: Attenuation tomography: an application to gas- hydrate and free-gas detection . Geophysical Prospecting, 55 , pp. 655-669. Rossi G., Chadwick R. A. andWilliams G. A.; 2011: Traveltime and attenuation tomography of CO 2 plume at Sleipner . Expanded Abstracts, EAGE Annual Meeting, A039. Vesnaver A., Iqbal M., Bouzidi Y., Bruno P. P. and Ali M. Y.; 2016: First Results from the EAGE Middle-East BootCamp Seismic Survey in the Jebel Hafeet Area . Expanded Abstracts, ADIPEC Conference, SPE-183276-MS. Vesnaver A. and Böhm G.; 2000: Staggered or adapted grids for seismic tomography? The Leading Edge, 19 , pp. 944-950. Vesnaver A., Böhm G., Madrussani G., Petersen S. and Rossi G.; 1999: Tomographic imaging by reflected and refracted arrivals at the North Sea . Geophysics, 64 , pp. 1852-1862.