(a) The surface elevations, (b) shear wave speed anomalies (δlnVS) and (c) shear wave speeds (VS) along profile A (Fig. 1). In b, black dashed lines mark a depth of 250 km and the 410 and 660 discontinuities, and white lines represent δlnVS contour levels from −4 to −2% and from 2 to 4% at 1% intervals. In c, black circles denote the seismicity, VS are plotted with 4 × of vertical exaggeration (VE=4 × ), and white lines represent δ ln VS contour levels from 2 to 4% at 1% intervals extracted from b. In b and c, grey dashed line delineates the Moho from CRUST2.0 (ref. 25). The abbreviations of rift zones, NLR, XGR, TYR, PXR, YGR and CR, and the different lithospheric block, IL, TL and AL are defined in the text block on the right.