GNGTS 2013 - Atti del 32° Convegno Nazionale

by sinkholes since 1993. Consequently an efficient predictive model taking into account the hydrogeology and hydraulic context, especially the occurrence of rains and sea storms, must be produced. References Anderson, M.P. and Woessner W.W.; 1992: Applied Groundwater Modeling. Academic Press, Inc., San Diego, 381 pp. Calò P., Macrì F., Piccinni F. and Tinelli R.; 2011: Instabilità del centro urbano di Casalabate (Lecce, italia): analisi delle condizioni di rischio - Instability of Casalabate village (Lecce, Italy): analisys of risk conditions. Italian Journal of Engineering Geology and Environment, 11(1), 55-64. Conyers L.B. and Goodman D.; 1997: Ground-penetrating radar – an introduction for archaeologists. Alta Mira Press. Conyers L.B.; 2004: Ground-Penetrating Radar for Archaeology. (Walnut Creek, CA: Alta Mira). Delle Rose M. and Fiorito F.; 2000: Ipotesi di recupero del territorio di Casalabate. Economia e Società, 2, 71-81. Delle Rose M. and Federico A.; 2002: Karstic phenomena and environmental hazard is Salento costal plains. Proc. IX IAEG Congress, J.L. van Rooy and C.A. Jermy editors, Durban, 1297-1305. Delle Rose M. and Leucci G.; 2010: Towards an integrated approach for characterisation of sinkhole hazards in urban environments: the unstable coast site of Casalabate, (Lecce, Italy). Journal of Geophysics and Engineering, 7, 143-154. Geostudi Astier; 2010: ErtLab Solver – Release 1.3.1. Loke M.H.; 2011: Tutorial: 2-D and 3-D electrical imaging surveys. www.geoelectrical.com Margiotta S., Negri S., Parise M. and Valloni R.; 2012: Mapping the susceptibility to sinkholes in coastal areas, based on stratigraphy, geomorphology and geophysics. Nat. Hazards, 62, 657–676. Pazdirek O. and Blaha V.; 1996: Examples of resistivity imaging using ME-100 resistivity field acquisition system. EAGE 58th Conf. and Technical Exhibition Extended Abstracts, Amsterdam. Reynolds J.M.; 2011: An Introduction to Applied and Environmental Geophysics, John Wiley & Sons Ltd., Baffins Lane, Chichester, second edition. Rossi D.; 1969: Note illustrative della Carta Geologica d’Italia. Fogli 203, 204, 213 – Brindisi, Lecce, Maruggio. Servizio Geol. It., 42 pp. A new methodology to estimate the EM velocity from Common Offset GPR: theory and application on synthetic and real data M. Dossi 1 , E. Forte 1 , M. Pipan 1 , R.R. Colucci 2 1 Department of Mathematics and Geosciences (DMG), University of Trieste, Italy 2 Institute of Marine Sciences (ISMAR), National Research Council (CNR), Trieste, Italy Introduction. A good EM wave velocity model is an important parameter in various GPR processing and analysis steps, such as depth conversion, data imaging and extraction of qualitative/quantitative information about subsurface lithology and fluid content. Unlike the seismic reflection case, where the velocity model is estimated from data collected with multiple source-receiver offsets, most GPR data acquisitions are performed with a single receiver antenna, so that the acquisition of multi-offset datasets is extremely demanding (Pipan et al. , 1999). Therefore the velocity field used for radar imaging is most often a constant value or, less frequently, a single approximated velocity function of depth [v(z)], obtained by analyzing single common midpoint (CMP) gathers. In most subsurface conditions, such model is inadequate to produce correct images even for qualitative studies. Multi-channel GPR systems present numerous advantages, such as significantly reduced 3-D survey times by simultaneously collecting multiple profiles, or full multi-offset data measurement through multiple receiver antennas at different offsets. By processing such continuous multi-offset data gathering, it is possible to obtain an EM velocity model over the whole survey area (e.g. Moysey, 2011) with high horizontal resolution, while traditional single- channel GPR systems normally limit CMP data acquisition to only a few locations. Besides such advantages, multi-channel GPR systems have some logistical limitations related to their size, which prevent their application in indoor surveys, in remote areas unreachable by motorized vehicles (such as mountains or glaciers), or in areas with rough topography. Moreover, the velocity analysis, which can be performed on multi-offset GPR 112 GNGTS 2013 S essione 3.2