Record sections of vertical-component seismograms (a: MTr6-96, b: MTr6-79, c: MTr8-15, d: MTr8-7). Vertical axis represents travel time (s) with a reduction velocity of 8.0 km/s. Horizontal axis denotes the offset distance in km from the OBS. P
is the phase refracted through the crust, P
is the mantle refraction phase, P
is the later phase refracted through the crust, and P
P is the phase reflected at the Moho.