Fig. 7

Record section with theoretical travel times and ray diagrams for shot L1. a Record section on which travel time curves predicted from the velocity model (Fig. 5a) are shown. Theoretical travel times for first arrival and late phase are shown by a green and brown curves, respectively. See also the phase identifications in Fig. 6a. Phase “A” is interpreted to be Pn wave (refracted wave from the upper mantle), while phases “B” to “D” are are explained by superposition of PiP1 and PmP waves (reflected waves from the interfaces R1 and Moho, respectively). See also ray diagrams in c. b Record section on which travel time curves from a velocity model with 8-km deeper Moho (see c) are shown. Theoretical travel times for first arrival and late phase are shown by a green and brown curves, respectively. See also the phase identifications in Fig. 6a. Phase “B” in Fig. 6a is interpreted to be the PiP1 phase. The onset of wave train of phase “C” is explained by Pn wave while its later part by PmP wave. c Ray diagrams for PmP (light blue) and Pn (red) waves. Interfaces corresponding to PiP1 wave is indicated by R1. A broken curve shows the Moho location 8 km shifted downward (see the text for detailed explanation), which corresponds to the case of b