Secular and tidal strain across the main ethiopian rift

Roger Bilham, R. Bendick, K. Larson, P. Mohr, J. Braun, S. Tesfaye, L. Asfaw

Research output: Contribution to journalArticlepeer-review

141 Scopus citations

Abstract

Using a combination of laser ranging and GPS data acquired between 1969 and 1997 we derive a separation velocity for the Somali and Nubian plates in Ethiopia (4.5±1 mm/yr at N108±10E). 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 μstrain/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.

Original languageEnglish
Article number1998GL005315
Pages (from-to)2789-2792
Number of pages4
JournalGeophysical Research Letters
Volume26
Issue number18
DOIs
StatePublished - Sep 15 1999

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