Figure 10 Vertical profiles of the P-wave velocities in our
tomography result. (a) Blue dashed lines labeled b-g show the locations
of profiles in (b-g). Map features are the same as in Figure 4. (b-g)
P-wave velocity profiles. Black lines denote the Moho interface in
LITHO1.0 (Pasyanos et al., 2014). Note the different color bar for
profiles (f) and (g).
In contrast to the smooth patterns in the initial model LITHO1.0 in the
lower crust and uppermost mantle, strong small-scale anomalies can be
seen in our final 3-D P-wave velocity model. Although the depth
variation of P-wave speed in the lower crust and uppermost mantle may be
complex, regional variation seems consistent at different depths. For
instances, the stable Sichuan Basin always exhibits a smooth
high-velocity pattern in both the lower crust and uppermost mantle,
except for a slightly low-velocity zone between the depths of 50 km and
60 km (Figure 9). The eastern part of the Songpan-Ganzi Block shows
low-velocity extending from 55-km to 65-km depth; high-velocity areas
across the Longmenshan Fault Zone along 32°N can be seen in the depth
range of 50-65 km with a slight shift to the southeast of the fault.