Rayleigh wave tomography, Tanzanian craton

Phase velocities within the Tanzanian craton boundary and rifts (left). Phase velocities are compared to previous studies in the Canadian Shield (right). Flattening of the phase velocity curve within the Tanzanian craton region for periods between 50 and 100 s indicates the presence of a low velocity zone.




Phase velocity maps for 50 s period. Two-dimensional phase velocity variations using starting model shown on left. Deviations from the starting model are observed in the southeast corner of the Tanzanian craton boundary where the high velocity lithosphere has been disrupted. Low velocities are observed beneath the Kenya rift and south of the cratat the northern tip of Lake Malawi.



Shear wave velocity profile showing a pronounced low velocity zone beneath a high velocity lithospheric lid in the Tanzanian craton. The thin solid line shows our starting model (ak135). The rifts show low shear wave velocities at depths down to 150 km associated with high temperatures and partial melt.


Shear wave velocity cross sections (A-A' and B-B' shown in maps above) through the Tanzanian craton. The base of the high velocity cratonic lithosphere is resolved near 150 km depth. Low velocities associated with the Kenya rift and Western rift branch have light shading. Disruption of the southeast corner is observed within the cratonic lithosphere near B' and in the phase velocity maps above.