GNGTS 2018 - 37° Convegno Nazionale

630 GNGTS 2018 S essione 3.2 GEOPHYSICAL CHARACTERIZATION OF URBAN UNDERGROUND OF THE AVIGLIANO TOWN (SOUTHERN ITALY) G. Calamita 1 , S. Piscitelli 1 , A. Perrone 1 , V. Serlenga 1 , T.A. Stabile 1 , M.R. Gallipoli 1 , J. Bellanova 1 , M. Bonano 1,2 , F. Casu 2 , L. Vignola 3 1 Institute of Methodologies for Environmental Analysis, National Research Council (CNR-IMAA), Tito (PZ), Italy 2 Institute for electromagnetic sensing of the environment, National Research Council (CNR-IREA), Napoli, Italy 3 National Association for Public Assistance (ANPAS), Marsicovetere (PZ), Italy Introduction. An renewed awareness of the urban subsoil as energy resource or as a space for hosting infrastructures has recently been growing (Mielby et al., 2016). Improved exploration, characterization and modelling approaches are required in line with this view (Showstack 2014). Thanks to the diverse range of mature exploration methodologies, applied geophysics holds a valuable potential for the collection of spatially distributed data that can be both combined with each other and with data derived from direct surveys. A wide variety of environmental and engineering issues has already been tackled and solved by means of geophysical-based approaches, especially in rural areas. In fact, the urban environment imposes strong constraints not only on invasive direct surveys, which still provide valuable indications although limited in terms of spatial scale (Lapenna 2017), but also on geophysical surveys, in terms of data quality deterioration and logistics. Nevertheless, geophysics has already been applied in urban contexts to assess site amplification effects (Mucciarelli et al., 2011), to estimate the fundamental frequencies and damping of buildings (Gallipoli et al., 2009), to detect shallow cavities in historical areas (Piscitelli et al., 2007), to delineate fracture zones (Mehta et al., 2017), to detect causes of subsidence effects (Solari et al., 2017) and to monitor subsurface leakage in industrial/nuclear areas (Kuras et al., 2016). In the framework of an agreement between the Institute of Methodologies for Environmental Analysis (IMAA) of the Italian National Research Council (CNR) and the Soil Protection Office of Basilicata Region, a methodological approach successfully applied by other authors in rural context (Perrone et al., 2006) is here tested in a urban environment with the aim to support the diagnostic and monitoring of instability phenomena affecting the Avigliano (PZ) town (Basilicata Region, southern Italy). The approach is based on a top-down philosophy where satellite and ground-based techniques are applied in a coordinated way. Materials and Methods. The urban area of Avigliano and the surrounding areas are heavily affected by ancient and recent multiple and complex roto-translational-earthflows, periodically undergoing to partial or total reactivation. Moreover, heavy damages to buildings and facilities in the urban area are caused by significant instability phenomena affecting the most superficial and altered layer of sands formations or slope debris layer abundantly reported the area. In this paper the focus is on the sector located near Via Roma (40.729608 N, 15.719757 E) which has long been affected by such phenomena, due to differential failures of detrital nature of the material used to fill an old channel (Fig. 1). In order to achieve a characterization of the site as accurate as possible, a top-down approach was applied by using a suite of geophysical methods. Firstly, satellite SAR data, for the period march 2012-september 2015, were analyzed by means of the Small BAseline Subset (SBAS) differential interferometric (DInSAR) algorithm (Bonano et al. 2012) to highlight the superficial deformations at a larger scale. Then, between June 2016 and February 2017, the following in- situ geophysical survey methods were applied (Fig. 1): • N. 5 Electrical Resistivity Tomographies (ERT) using a Syscal Pro geo-resistivimeter (IRIS Instr.); • N. 1 refraction seismic profile using a seismograph (Geometrics) with 14 Hz geophones (Geospace); • N. 1 active seismic array Multichannel Analysis of Surface Waves (MASW) using a Geode seismograph (Geometrics) and 4.5 Hz geophones (Geospace);