Fig. 5

a Seismograms produced by the 9th source excitation at 0 m distance (shot_0m) as recorded in 24 geophones (g1–g24). Inset shows the amplitude saturation in recordings of the first geophones (g1–g4), which were discarded from the analysis. b Phase velocity stack values (different colors) and phase velocity estimates (black symbols). Red colors correspond to the largest velocity stack values. Black curve connects stack peaks to form the phase velocity dispersion curve of the fundamental mode of Rayleigh waves