Methodologies of study for the development in the subsoil of an urban coastal area, for example Naples

The expansion in the subsoil of an urban coastal area can interest both the inshore and the offshore. The three-dimensional geological model has to include both the areas using geological unity that represents them. The methodologies of investigation for collecting subsoil geological data vary greatly in relation to the local geological characteristics and the available funding. Usually inshore explorations in urban area are mainly based on mechanical drilling (boreholes), while coastal offshore investigations are based on seismic high resolution reflection. The old part of the urban area of Naples is developed along a coastal zone whose geology is the result of a complex interaction among tectonics, eustatic variations, climatic variations, volcanism and volcano tectonics. It is developed on a skeleton (bed rock) constituted by a yellow tuff (Neapolitan Yellow Tuff deposit). The subsoil of Naples has been used since its foundation in the 900 B.C., for different functions. Today a new metropolitan line has been completed along the coastal and/or paleo-coastal line. Currently a project aimed at realizing a tunnel that by-passes the coastal area characterized by a long tract offshore is being discussed. The study of the subsoil of the coastal area inshore in Naples has been made by studying the data of preexisting boreholes. Starting from the litologies described in the stratigraphy of the holes, litofacies and facies associations have been deduced and consequently the principle sedimentary architectures have been reconstructed. The study in offshore area has been conducted using high resolution reflection seismic profiles acquired in proximity of the Neapolitan coast. The analysis of these profiles, combined in some areas with the results of magnetometric investigation, has allowed for the recognition of the principal seismic facies characterizing the subsurface of the area and their geometry.We decided to use sequential units for the construction of a geological model including inshore and offshore subsurface of the town. These units have been recognized from the compared studies of inshore and offshore facies associations and sedimentary architectures.