Multicomponent Seismic Profiles in Galleries Excavated in a Clay Layer at Tournemire (France)

We performed seismic measurements in two 130m and 70m long galleries and one vertical 160m deep borehole of the IRSN Tournemire experimental station. Vertical and horizontal microvibrators and a sledgehammer were used as a seismic source and three-component geophones for recording the data. We determined the seismic velocities in Toarcian clay at Tournemire for horizontally and vertically propagating waves by recording seismic data in the tunnel galleries and in a zero-offset VSP. The qP wave propagates with 3400 m/s (vertical) and 3000 m/s (horizontal), the qSV wave with 1300 m/s, and the SH wave with 1300 m/s (vertical) and 1900 m/s (horizontal). These values correspond to anisotropy parameters epsilon = 0.14 and gamma = 0.57.