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Different physical mechanisms have been put forward in order to explain the lithospheric evolution beneath a continental rift. Models of stretching of the lithosphere, though giving good values for the trough subsidence, could not satisfactorily account for other features of the rifts, such as the rapid uplift of the rift shoulders in some cases. However, the idea that the thinning of the lithosphere is also accomplished by secondary convection phenomena is now receiving growing attention. Using a thermomechanical model dealing with a non-Newtonian crust and mantle, Moretti and Froidevaux have suggested that the evolution of numerous continental rifts is the consequence of the combination of the upward propagation of an asthenospheric thermal anomaly and of an extensional regional stress. The Suez rift evolution, examined by tectonic subsidence studies, may be regarded as the result of an asthenospheric upwelling and of a short active initial lithospheric stretching phase.

The overall structure of rifts is often controlled by normal faults and tilted blocks. In several rifts the crests of the blocks have been strongly eroded while the associated half-graben has undergone large subsidence. The relative movement of the crest of a block can be analysed assuming simple circular geometry of its bounding fault. In such a geometric model, subsidence of the half-graben and relative uplift of the crest are connected and this coupling can be quantified as a function of the fault shape and of the block width. Knowing the geometry of a fault, we can calculate the movements of a rigid block rotating along this fault. Inversely, by knowing the tilting of a block, it should be possible to estimate the geometry of the guiding fault, i.e. its detachment depth, if we assume the fault to be listric. Numerical results show that a large block can undergo an absolute uplift. The direction of the movement depends on the initial width of the block and is quite independent of the tilt angle, except for very low-angle faults.

A three-dimensional study of the structure of the Suez rift has been carried out using field and subsurface data, in an attempt to determine the role of transverse faults and the longitudinal evolution of the rift.

We report the results of fifteen Expanding Spread Profiles (ESP's), and a seismic wide angle reflection-refraction Une, performed during March–April 1986, in the Gulf of Suez and the Egyptian part of the northern Red Sea area (north of 25°N). Four 16.4 air guns were used as a sound source on board R.V. “Le Suroit” and a 96-channel 2.4-km long streamer was towed by a supply vessel, the “Whity Tide”. Most of the profiles show good crustal reflection and refraction arrivals and often good Moho arrivals obtained for a distance of 80 to 100 km. We present the results of X- Tand τ- panalysis, obtained by a velocity inversion performed in the τ- pplane and by ray-tracing modeling of both the τ- pand the X- Tsections. The velocity models are computed for planar and linear gradient velocity layers.