One-dimensional shear velocity structure of Northern Africa from Rayleigh wave group velocity dispersion

Rayleigh wave group velocity dispersion measurements from 10 s to 160 s per iods have been made for paths traversing Northern Africa. Data were accumul ated from the IRIS DMC, GEOSCOPE, and MEDNET seismic networks covering the years 1991-1997. The group velocity measurements are made including the eff ects of debiasing for instantaneous period and a single-iteration, mode-iso lation (phase match) filter. The curves are grouped by tectonic province an d compared to tomographic model-based curves in an effort to test and valid ate the tomographic models. Within each tectonic category (rift, orogenic z one, or craton) group velocity curves from various provinces are similar. B etween tectonic categories, however, there are marked differences. The rift related paths exhibit the lowest group velocities observed, and cratonic p aths the fastest. One-dimensional shear velocity inversions are performed, and while highly nonunique, the ranges of models show significant differenc es in upper mantle velocities between the tectonic provinces. This work is part of a larger project to determine group velocity maps for North Africa and the Middle East. The work presented here provides importan t tools for the validation of tomographic group velocity models. This is ac complished by comparing group velocity curves calculated from the tomograph ic models with carefully selected high-quality group velocity measurements. The final group velocity models will be used in M-S measurements, which wi ll contribute to the m(b):M-S discriminant important to the Comprehensive N uclear-Test-Ban Treaty (CTBT). The improved shear wave velocity models prov ided by this study also contribute to the detection, location, and identifi cation of seismic sources.