First two‐station results for long‐period surface waves velocity from the Geoscope Stations in Africa

Abstract

Rayleigh and Love phase and group velocity dispersion measurements are performed along a purely african path between the Geoscope stations TAM and AGR, for the Leewards Isl. earthquake of March 16, 1985. This regional study is important as it brings deep‐seated structure information in a seismologically blank region of Africa. It enables to improve the spatial resolution of larger scale models. For periods longer than 160 s. and up to 250 s., the fundamental Rayleigh wave dispersion is in agreement with prediction by global models. For shorter periods, the results fall below this prediction, which is an indication of lithospheric S‐wave velocities lower than those of the models. The results are also compared with previous regionalizations. The Rayleigh second higher mode is extracted at AGR, and the phase velocity dispersion obtained in the period range 50‐140 s is in agreement with the theoretical dispersion for PREM.