CRUSTAL STRUCTURE ALONG A TRAVERSE ACROSS THE MIDDLE AND HIGH ATLAS MOUNTAINS DERIVED FROM SEISMIC REFRACTION STUDIES

In 1986 explosion seismic investigations have been carried out along a traverse of about 350 km length running from NNW to SSE crossing the High and Middle Atlas. Two further profiles run E/W through the Middle and NW-SE through the High Atlas. Neither the High nor the Middle Atlas mountains have a significant root. The maximum thickness of crust with 38-39 km is found under the northern border of the High Atlas. South and north of the High Atlas the crustal thickness amounts to 35 km. The upper as well as the lower crust are strongly structurized in the vertical direction. Significant for the profiles observed is the change between high and low velocities in the whole crust. The velocities at the uppermost mantle are relatively low with values of 7.7-7.9 km/s. The average velocities for the whole crust are 6.1-6.2 km/s.