The T phase of shallow-focus earthquakes*

Abstract

A short-period phase, 0.5 sec. period or less, traveling through the ocean with the velocity of sound in water has been identified on a large number of seismograms of earthquakes occurring at sea. This arrival was identified on the Benioff short-period seismograms of the Weston, Fordham, and Ottawa stations for a series of Dominican Republic shocks, and on the Benioff short-period seismograms of the Pasadena network of stations and the Mount Hamilton and Mineral stations for a series of major Japanese and Aleutian shocks. The existence of this phase had been noted previously by Linehan, who was at a loss to provide an explanation for them. The mechanism of propagation of the T phase is discussed and several practical applications are described.