Crust and upper mantle P- and S-wave delay times at Eurasian seismic stations

Abstract

Median crust and upper mantle P- and S-wave delay times, based on residuals for teleseismic P- and S-wave arrival times included in the groomed ISC/NEIC database of Engdahl et al. [Bull. Seism. Soc. Am. 88 (1998) 722] are estimated as functions of time and azimuth for Eurasian seismic stations. The effects of source and lower mantle 3-D structure on the station residuals are corrected by ray tracing all phase data (to a depth of 400 km below the station) through the 3-D P- and S-wave models of Bijwaard et al. [J. Geophys. Res. 103 (1998) 30055] and Bijwaard [Seismic travel-time tomography for detailed global mantle structure. University of Utrecht, Utrecht, The Netherlands, 1999, 179 pp.], respectively. In general, crust and upper mantle P- and S-station delays based on medians of azimuthally binned residuals are spatially coherent and can be qualitatively associated with Eurasian tectonic features such as orogens and cratons, as well as with structural elements such as sediment and crustal thickness, and average uppermost mantle velocities. Paired P- and S-station delays are correlated with a rather poorly determined slope (S/P delay time ratio) of about 1.9.