Deformation across the Asal‐Ghoubbet Rift, Djibouti, Uplift and crustal extension 1979–1986

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Abstract
Geodetic networks of different sizes have been established since 1973 in the Asal‐Ghoubbet rift in south‐western Afar in order to study crustal movements across an extensive plate boundary. Partial or entire remeasurements of these networks during the 1979–1986 interval provide detailed data about strain accumulation and vertical movements after a seismo‐volcanic rifting event that occured in November 1978 along this area similar to an oceanic accreting plate boundary. The results of the geodetic monitoring indicate a continuous opening of the rift zone of about 6 cm/yr since 1979. The deformation is principally distributed in the Inner Floor of the rift with a uniaxial extensional N40°E strain rate of about 15 µstrain/yr. The results of the 1979 and the 1984–85 levellings define the development of a large uplift across the rift zone amounting 15 cm during this 6 year interval. This uplift is accompanied with a relative collapse of the Inner Floor zone of about 4 cm which is associated with creep on the active faults bounding the rift. Two stages of the rifting process are successively observed in Djibouti: an abrupt rifting event in 1978 and then a continuous accumulation stage which is controled by the plate motion and partially by magmatic inflation and active creep faulting.