Contributions of borehole seismics in the geometric modelling of subsoil in the underground fixtures area of Modane (Savoie, France)

In the framework of the Lyon-Turin railway project, a 52 km long basis tunnel between Saint Jean de Maurienne (Savoie, France) and Susa (Piemont, Italy) is planned (Fig. 1). An underground service and assistance station rnid-tunnel is designed around 400 metres in depth, on the right side of the Arc river, under the Avrieux sector. Because of the importance of this area, also called the underground fixtures area, and the complexity of the geological context, many boreholes have been drilled with well logging measurements and many seismic surveys have been carried out. The joint interpretation of these different types of data and their specific processing leads to precise structural and hydrogeological models of this area which are of great importance for the construction of the tunnel.