Seismic travel time anomaly due to anomalous heat flow and density

The effects on seismic travel times of (1) excess temperatures associated with the low-order harmonics of the surface heat flow and (2) excess mass estimated from the high-order harmonics of the earth's gravitational field as determined from satellite orbits are calculated. The results are compared with the data of heat flow and the seismic time delays of Longshot, an underground nuclear explosion in the Aleutians. It is suggested that the thermal field rather than the density of the earth may be a major cause of the seismic travel time anomaly.