GNGTS 2019 - Atti del 38° Convegno Nazionale

550 GNGTS 2019 S essione 3.1 of 5 to 10 degrees (Fig. 1). In Figure 2b (left panel) two data examples of the rotated horizontal components are displayed in the shot sections of the active seismic profile P01. Results. The majority of the refraction seismic data show mantle phases at offsets up to 70 km. We observe a first arrival phase up to 20 to 25 km with an apparent velocity of 4.6 km/s without a strong velocity gradient that is interpreted as sedimentary units. Further, a very prominent wide-angle reflection originates from the crust mantle boundary and has an apparent velocity of 8 km/s. It occurs up to distances of 70 km. Its features share a number of characteristics (i.e. offset range, continuity) generally associated with continental settings rather than mimicking seafloor spreading lithosphere emplaced in back-arc basins. Based on traveltime tomography, first velocity profiles have been developed along the wide- angle refraction profiles. Along profile P02, the velocities have been converted into densities and the gravity Free Air Anomaly response was calculated and compared to the measured gravity field from satellite data. Our results are compared to a previously acquired profile that continues from P01 in north-east direction to the Italian coast. The crust-mantle boundary in the centre of the Ligurian Basin is determined at ~9.5 km depth below the seafloor. The acoustic basement is difficult to map seismically. Seismic phases indicate the transition to the crystalline crust in the southern part of the profile at a depth of ~6.5 km below the seafloor. The nature of crust in the central part of the Ligurian Sea is still under discussion. The absolute seismic velocities and the observed velocity gradients can be interpreted as hyper-extended continental crust or serpentinised oceanic mantle. The thick sedimentary coverage allows for long lasting extension of the crust. The crustal portion interpreted from the seismic velocities thickens towards the north which is in good agreement with the anti-clockwise rotation of the Corsica-Sardinia block and an associated gradual opening and extension of the Ligurian Basin. AMBIENT SEISMIC NOISE TO IMAGE AND MONITOR THE PROPAGATION MEDIUM ELASTIC PROPERTIES IN GEORESOURCE EXPLORATION AND EXPLOITATION AREAS P. Forlenza 1 , M. Vassallo 2 , O. Amoroso 1 , R. De Matteis 3 , V. Convertito 4 , P. Capuano 1 1 Dipartimento di Fisica “E.R. Caianiello”, Università Degli Studi Di Salerno, Fisciano (SA), Italy 2 Istituto Nazionale di Geofisica e Vulcanologia, L’Aquila, Italy 3 Dipartimento di Scienze e Tecnologie, Università Degli Studi Del Sannio, Benevento, Italy 4 Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Napoli, Italy Introduction. In seismology traditional methods for the study of the Earth structure are based on the information that can be extracted from direct waves emitted by seismic sources such as earthquakes or explosions. Useful information about the Earth interior, that is not directly available, can also be contained in the ambient seismic noise. In the last decade, the interest in these alternative methods has grown because they are particularly advantageous both for economic reasons and for overcoming some limitations of the traditional techniques, in particular: localized natural or artificial sources are not needed; ambient seismic noise analysis can be used to assess the aseismic response of the subsurface; the newmethod enhances resolution because measurements are made between regularly spaced receivers, which may lie much closer to one another than to earthquakes (Shapiro et al. , 2005). The purpose of this work is the application of methods based on ambient noise analysis to the areas where unconventional hydrocarbons extraction takes place that can originate