Surface Deformation Associated With a Historical Diking Event in Afar From Correlation of Space and Air-Borne Optical Images.

摘要

We present new measurements of the surface deformation associated with the rifting event of 1978 in the Asal-Ghoubbet Rift, Republic of Djibouti using an optical image correlation technique. Deformation in the rift associated with the event included the reactivation of the main bordering faults and the development of numerous open fissures on the rift floor. We combine these new measurements with ground-based observations from previous work to constrain a kinematic model of the rift consisting of two bordering faults reaching a depth of 3 km and a vertical dike below this depth. Our modeling indicates that the horizontal extension collectively accommodated by the faults and fissures amounts to 2.4-2.8 m, significantly higher than the amount of ∼1.2 m estimated by trilateration alone over a ∼10 km baseline. The model suggests that during the 1978 event, magmatic fluids were transferred from a mid-crustal reservoir to the shallow structures, injecting dykes and filling faults and fissures, reaching the surface in the Ardokoba fissural eruption.