(a) The surface elevations, (b) shear wave speed anomalies (δlnVS) and (c) shear wave speeds (VS) along profile B (Fig. 1). (d) The surface elevations, (e) δlnVS and (f) VS along profile C (Fig. 1). In a and d, vertical red bars indicate major fault zones. In b and e, black arrows mark the Main Frontal Thrust (MFT) and suture zones (IYS, BNS, JS and AKMS) and white lines represent δlnVS contour levels from −4 to −2% and from 2 to 4% at 1% intervals. In c and f, black circles denote the seismicity, VS are plotted with 4 × of vertical exaggeration (VE=4 × ), black dashed lines mark a depth of 250 km and the 410 and 660 discontinuities, and white lines represent δlnVS contour levels from 2 to 4% at 1% intervals extracted from b and e, respectively. In b,c,e and f, grey dashed lines delineate the Moho from CRUST2.0 (ref. 25) and thick magenta lines represent the interpreted upper interface of underplated IL with a dip angle of 10°.