Fig. 3

Horizontal section across 3-D P-wave tomographic model of Diehl et al. (2009) at a depth of 20 km. Yellow triangles indicate seismic stations used for tomographic inversion, crosses indicate inversion grid nodes. Note that the velocity structure is shown as percentage change relative to the 1-D initial reference model rather than in terms the P-wave velocities shown in Fig. 2. Bold black contours include well-resolved regions covering most of the area depicted. Compare Fig. 1 for major tectonic units outlined: RSL Rhone-Simplon Line, PL Periadriatic Line, PF Penninic Front, ACL Argentera-Cuneo Line. Comparison with Fig. 2 shows that the entire area with P-wave anomaly >10%, as well as a part of the area with P-wave anomaly >5% between north of Locarno and Cuneo is within the Ivrea mantle wedge