Secular and tidal strain across the main Ethiopian rift

This vector is orthogonal to the NNE-trending neotectonic axis (Wonji fault belt) of the Ethiopian rift axis. Current rifting is concentrated within a 33-km-wide zone that includes a 7-km-wide belt of late Quaternary faulting where maximum surface strain rates are comparable to those at active plate boundaries (0.1 mu strain/yr).

The strain-field suggests that thin (<5 km) elastic crust separates thick continental lithosphere, a geometry quite different from oceanic rifting, and a mechanical configuration that favors the amplification of regional strain. Semidiurnal strain tides, however, as measured by kinematic GPS methods are not amplified along or across the rift, indicating that the rift zone's low rigidity applies only at periods of years.