GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 3.2 629 García-Jerez A., Piña-Flores J., Sánchez-Sesma F.J., Luzón F. and Perton M.; 2016: A computer code for forward calculation and inversion of the H/V spectral ratio under the diffuse field assumption . Computers & Geosciences, 97 , 67-78. LeBrun B., Duval A.M., Bard P.-Y., Monge O., Bour M., Vidal S. and Fabriol H.; 2004: Seismic Microzonation: A Comparison between Geotechnical and Seismological Approaches in Pointe-à-Pitre (French West Indies) . Bull. Earthq. Eng., 2 , 27-50. Marinos P. and Hoek E.; 2001. Estimating the geotechnical properties of heterogeneous rock masses such as Flysch . Bull. Engg. Geol. Env., 60 , 85-92. Milli S., Moscatelli M., Stanzione O. and Falcione F.; 2007: Sedimentology and physical stratigraphy of the Messinian turbidite deposits of the Laga Basin (central Apennines, Italy) . Ital. J. Geosci., 126(2) , 255-281. Nakamura Y.; 1989: A method for dynamic characteristics estimation of subsurface using microtremor on the ground surface . Quarterly Report of Railway Technical Research Institute (RTRI), 30(1) , 25-33. TOMOGRAPHIC CHARACTERIZATION OF A SHALLOW AQUIFER BY P-WAVE VELOCITY AND Q FACTOR P.P. Bruno 1 , A. Vesnaver 2 1 Dipartimento di Scienze della Terra, Ambiente e Risorse, Università di Napoli Federico II, Italy 2 Istituto Nazionale di Oceanografia e Geofisica Sperimentale, Sezione di Geofisica, Trieste, Italy Introduction. The characterization of fluid-saturated porous rocks is a key challenge not only for hydrocarbon production, but also for fresh water catchment and geothermal energy generation. Two relevant parameters for modeling the fluid flow in porous media are the porosity and permeability of rocks, which must be estimated for a large 3D volume encompassing the saturated formation. Seismic reflection tomography (or the more expensive full-waveform inversion) can provide an accurate depth model for P and S velocity, whose correlation with porosity and acoustic impedance is often satisfying. Instead, the permeability is a very elusive parameter to estimate using a single, (i.e. static) seismic survey, unless the survey is repeated over time intervals using sophisticated time-lapse analysis tools. Time-lapse seismology is very expensive and not always conclusive. For these reasons, we tested a coupled tomographic inversion of P velocity and Q factor to process a high-resolution seismic profile acquired, in the Al Jaww Plain (close toAl Ain), where the largest producing aquifer in the UnitedArab Emirates is located. The goal is a better characterization of the rock properties, including permeability, as Q factor and seismic reflectivity can integrate the velocity anomalies, providing geologists and environmental engineers with additional parameters to build quantitative Earth models. As (training) seismic dataset we used a high-resolution seismic profile acquired in November 2015 in the Al Jaww plain (United Arab Emirates) during the First EAGE Middle East Bootcamp, co-organized by the Petroleum Institute of Abu Dhabi, ADNOC and Schlumberger. Geological settings. Al Jaww Plain extends for ~500 km 2 to the southeast of the town of Al Ain and it is bounded to the east by the western margin of the northern Oman Mountains. This plain, which provides a considerable share of Abu Dhabi’s fresh water resources, is mostly covered with Quaternary sediments ranging from alluvial deposits, desert plain deposits, sabkha deposits and aeolian sand. Surface drainage on the piedmonts and alluvial fans subdivisions are generally canalized in wadies with variable flow patterns exhibiting complexly braided channel morphologies (Menges and Woodward, 1993). Al Jaww sedimentary basin can be roughly divided into two parts affected by different tectonic conditions. The older part of the basin consists of a sedimentary sequence deposited on a rifted margin over a Precambrian crystalline basement. The younger sediments locate on the top of the previous sequence, and result from