Ability of High-Resolution Resistivity Tomography to Detect Fault and Fracture Zones: Application to the Tournemire Experimental Platform, France

摘要: The Experimental Platform of Tournemire (Aveyron, France) developed by IRSN (French Institute for Radiological Protection and Nuclear Safety) is composed a tunnel excavated in an argillite formation belonging to limestone–argillite–limestone subhorizontal sedimentary sequence. Subvertical secondary fault zones were intercepted using drifts boreholes the at depth about 250 m located under Larzac Plateau. A 2D 2.5 km baseline large-scale electrical resistivity survey conducted 2007 allowed detecting upper limestones several significantly low subvertical (Gelis et al. Appl Geophys 167(11): 1405–1418, 2010). One these discontinuities consistent with extension towards surface identified from tunnel. In attempt better characterize this zone, MINES ParisTech high-resolution transversally fracture zones. 760-m-long profile was acquired two array geometries take-outs 2, 4 8 m, requiring roll-alongs. These data first inverted independently each take-out then all together given geometry. Different models display same global features high (higher than 5000 Ωm) (lower 100 are finally compared geological cross-section based on independent data. conductive agreement locations inferred cross-section. Moreover, top more below zone between zones, sandy argillaceous layer. This interpreted as presence scattered could be correlated fractured 250-m underground works. study highlights interest multi-scale approaches image complex heterogeneous near subsurface layers. Finally, shows that tomography useful powerful tool detect limestones. Such method complementary other geophysical