Panels (a) and (b): Bouguer anomalies computed using a high definition DTM having a 250 m grid mesh, for a crust density of 3000 kg m−3, panel (a) and 2670 kg m−3, panel (b). Panels (c–f): Residual gravity anomaly computed assuming different values of crust density, mantle density and reference Moho depth. (c) Crust density 2670 kg m−3; mantle density 3270 kg m−3; reference crust thickness 30 km. (d) Crust density 3000 kg m−3; mantle density 3270 kg m−3; reference crust thickness 30 km. (e) Crust density 3000 kg m−3; mantle density 3400 kg m−3; reference crust thickness 30 km. (e) Crust density 3000 kg m−3; mantle density 3400 kg m−3; reference crust thickness 20 km. The light yellow zones in panel (e) indicate the envelope of the two set of profiles along which the comparative analysis is carries out. Black continuum lines indicate the profiles delimiting SEC 1 and SEC 2. The black arrows in panel (e) indicate the relative Africa–Eurasia velocities, as envisaged by the recent GPS data (Fernandez 2003), with a 90 per cent tolerance ellipse. 41PL in panel (c) stands for 41 Parallel Lineaments (see text for further explanation).
