ELLIPTICITY CORRECTIONS FOR SEISMIC PHASES

The advent of broad-band seismology has meant that use is being made o f a wide range of seismic phases, for many of which ellipticity correc tions have not been readily available, In particular, when many seismi c phases are used in location schemes, it is important that the system atic effects of ellipticity are included for each phase. An efficient and effective procedure for constructing ellipticity corrections is to make use of the ray-based approach of Dziewonksi & Gilbert (1976), as reformulated by Doornbos (1988), in conjunction with the rapid evalua tion of traveltimes and slownesses for a given range using the tau-spl ine procedure of Buland & Chapman (1953). Ellipticity coefficients hav e been tabulated for a wide range of seismic phases and are available in electronic form. The ellipticity correction procedures have been ex tended to include an allowance for diffraction phenomena. for example P-diff, S-diff diffracted along the core-mantle boundary. Corrections for additional phases can be generated by building the ellipticity coe fficients from suitable combinations of the coefficients for different phase segments.