Assume that the S velocity perturbations plotted at 150 km depth in Figure 1.7 extend throughout the uppermost 300 km of the mantle. Estimate how many seconds earlier a vertically upgoing S-wave will...

Assume that the S velocity perturbations plotted at 150 km depth in Figure 1.7 extend throughout the uppermost 300 km of the mantle. Estimate how many seconds

earlier a vertically upgoing S-wave will arrive at a seismic station in the middle

of Canada, compared to a station in the eastern Pacific. Ignore any topographic or

crustal thickness differences between the sites; consider only the integrated travel

time difference through the upper mantle.