The Density Ratio at the Boundary of the Earth's Core

A theoretical study is made of the behaviour of a P wave incident from the mantle on the boundary of the earth's core, with special reference to phase reversals. The results are given graphically in Fig. 2, which gives the conditions for given values of the angle of emergence e and the density ratio ?'/? or the ratio of the elastic parameters   at the core boundary. The dependence of the phase changes on the density ratio is clear; for instance for ?'/? = I (no density discontinuity) there is a change of phase both for e 55°, whereas for ?'/? 1.7 there is a change of phase only for e 0.34. A method for determining the density ratio by more complete observations of PcP is indicated. DOI: 10.1111/j.2153-3490.1954.tb01135.x