This research is to map lateral variations of the fine structure of seismic velocities in the upper mantle and to relate these variations to fundamental geodynamical processes. The technical basis for the investigation is the application of two theoretical techniques developed under previous NSF grants: the first uses long-period, SH-polarized ScS reverberations to image the vertical profile of mantle reflectivity along short arcs; the second is a general technique for extracting phase information in the form of frequency-dependent travel times from complex parts of seismograms and inverting this information to obtain earth structure. By means of the combined application of these two techniques to reflected and refracted seismic waves, the investigator will study individual seismic profiles in the upper mantle to determine structure, composition and dynamics.
