Earthquake-generated Rayleigh waves excite shock waves at the surface of the earth which propagate upward nearly vertically through the atmosphere as infrasound. The HF Doppler sounder is a sensitive tool for detecting and recording these infrasounds at ionospheric heights. By constructing electron density distributions from ionograms the propagation ray paths and delay times for the long-period waves can be determined. By using these data the dispersion curves for oceanic Rayleigh waves have been deduced. These curves are within 5% of the expected curve synthesized from data obtained from seismograms. Application of these data to the 1969 Kurile Island earthquake shows that it had a single source, while application to the 1968 Tokachi-Oki earthquake shows the existence of several sources.