Observed very long period Rayleigh‐wave phase velocities across the Canadian shield

summary. The recent Indonesian earthquake (1977 August 19;M_s=8.0) makes possible a direct determination of Rayleigh‐wave phase velocities at very long periods (200 to 300 s) over a pure shield path (College, Alaska‐State College, Pennsylvania) by the two‐station method. Results are in good agreement with previous models derived by regionalization of great‐circle phase velocities and discussed in a previous paper (Okal, Paper I). Great‐circle phase velocities computed at College and State College are correctly predicted by the models derived in Paper I, and further substantiate one of its main conclusions: no substantial structural differences between oceans and continents at depths greater than 240 km, are necessary to account for the presently available seismic data.