Panchromatic Quickbird image (0.5 m resolution) of the dam site after the blast (in 2011) with underground spillway and penstock shown by blue lines. Electrical tomography profiles are shown by dark violet point-lines (each point is the location of one electrode). H/V measurements are shown by coloured filled circles; colours according to measured resonance frequencies from 2.7 Hz in yellow (1D thickness of more than 40 m considering an average Vs ~500 m/s) to more than 5 Hz in red (1D thickness of less than 20 m for average Vs ~ 400 m/s; sizes of circles indicate the measured amplitude). Light blue dots show the location of piezometers. Dark blue dots are topographic measurements. Lower left corner: view of the downstream face of the dam made from the point marked by the yellow view angle.