Thickness of the Earth's Crust in Antarctica and the Surrounding Oceans: A Reply

Summary The paper of Evison, Ingham, Orr & Le Fort on the dispersion of earthquake waves traversing Antarctica has recently been criticized by Bentley & Ostenso and by Kovach & Press. The discovery that the crust of eastern Antarctica is of continental thickness whilst that of Marie Byrd Land is some 10 km thinner is accepted by these critics, but they object to the two‐layer and three‐layer models used in obtaining this result, and also to the values that were assigned to the velocity parameters. For detecting large differences in crustal thickness, however, the traditional simple models have not been invalidated by the advent of the digital computer, which comes into its own with subtler problems; but the velocities appropriate to a simple model are not necessarily those indicated by refracted waves. Kovach & Press also criticize the use of Love waves rather than Rayleigh waves for investigating the oceanic crust around Antarctica. Their arguments on this point carry the unsatisfactory implications that the average velocity in the oceanic crust ought to increase with the thickness, and that there should be gross regional departures from isostasy at sea.