4. Assuming that the P velocity in the ocean is 1.5 km/s, estimate the minimum and maximum water depths shown in Figure 1.8. If the crustal P velocity is 5 km/s, what is the depth to the top of the magma chamber from the seafloor? Hint: Remember that the times are for surface-to-reflector-to-surface paths (i.e., two legs between the surface and the reflector). jn tho chear modulus D 3.0 East WEst 3.5 Laver 24 4.0 AMC 4.5 Figure 1.8 An image of the axial magma chamber (AMC) beneath the East Pacific Rise near 1415'S abtained through migration processing of reflection seismic data (from Kent et al., 1994). The profile is about 7 km across, with the vertical axis representing the two-way travel time of compressional waves between the surface of the ocean and the reflection point. The sea floor is the reflector at about 3.5 s in the middle of the plot, while the magma chamber appears at about 4.0 s and is roughly 750 m wide. Shallow axial magma chambers are commonly seen beneath fast-spreading oceanic ridges, such as those in the eastern Pacific, but not beneath slow-spreading ridges, such as the Mid-Atlantic Ridge. Time (s)