Fig. 20

a Evolution of the wavefront in the case of strongly heterogeneous media. The station with a green star acts as the source, and the red triangles show the stations concerning the advancing wavefronts. Note the triplication effects around the low-velocity zones. b Histograms of passage time residuals for measurements at 10 s for Rayleigh waves, initially compared to a uniform reference model with a velocity of 2.8 km/s with great-circle paths, and after the inversion with 6 iterations of the subspace method with deviated paths. Taken from Fig. 4 of Saygin and Kennett (2012)