SS-wave sensitivity to upper mantle structure: Implications for the mapping of transition zone discontinuity topographies

Abstract

Studies of the depths of the upper mantle discontinuities have relied on the differential travel times between the SS wave and its precursors. We examine the effect of velocity heterogeneities on these differential travel time data. Ray-theory, which is used to correct these data for the effect of velocity heterogeneities, is shown to be inaccurate if the characteristic heterogeneity length scales are similar to those seen in regional models or if the station is near the SS wave radiation nodal plane.