Torsional overtone dispersion from correlations of S waves to SS waves

Abstract

This paper presents SH overtone dispersion data obtained by using the phase correlation method of Brune (1964). The data augment the set provided by longer-period spheroidal and toroidal mode data and travel-time data. A major advantage of the phase-correlation method over travel-time data is the elimination, to first order, of source effects and source-region bias. The overtone data are consistent with lower-order spheroidal overtone data indicating a base-line correction of 4.0 ± 0.9 sec to the S-wave travel-time data of Hales and Roberts (1970). These and other fundamental-mode and overtone data, travel-time data, and mass and moment of inertia comprise 497 gross earth data and represent one more step in the march toward a spherically averaged earth model.