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Pre- Co- and Post-dyking Deformation in the Dabbahu Rift Segment (Afar, Ethiopia) Observed with InSAR

Tim Wright(1), Atalay Ayele(2), Juliet Biggs(3), Eric Calais(4), Davide D'Aria(5), Cindy Ebinger(6), Ian Hamling(1), Derek Keir(1), Atalay Lewi(2), Andrea Monti Guarnieri(7), Paolo Pasquali(8), Julie Rowland(9), Anna Stork(10) and Gezahegn Yirgu(2)

(1) University of Leeds, Leeds, LS2 9JT, United Kingdom
(2) University of Addis Ababa, Science Faculty, Addis Ababa, Ethiopia
(3) University of Miami, Miami, Florida, United States
(4) University of Purdue, Purdue, Indiana, United States
(5) ARESYS s.r.l, Via Garofalo 39, Milano, Italy
(6) University of Rochester, Rochester, New York State, United States
(7) Politecnico di Milano, Via Ponzio, Milano, Italy
(8) Sarmap s.a., Cascine de Barico, Purasca, Switzerland
(9) University of Auckland, Faculty of Science, Auckland, New Zealand
(10) University of Oxford, Parks Road, Oxford, United Kingdom


In September 2005, a 60-km-long dyke, up to 8 metres thick, was intruded into the upper crust in Afar, Ethiopia. InSAR, seismicity and structural studies confirm that the entire Dabbahu rift segment was active in this episode. Modelling of co-dyking InSAR data, acquired by Envisat, suggests that 2.5 km^3 of magma was intruded between depths of 2 and 9 km, with 0.5 km^3 sourced from shallow magma chambers beneath Dabbahu and Gabho volcanoes at the northern end of the segment. ERS and Envisat Interferograms spanning time periods prior to the rifting episode show that Gabho began uplifting after September 2000, and that this may have been the trigger for the rifting episode. We installed 10 continuously recording GPS instruments in January 2006. Together with image mode and wide swath interferograms, these show rapid ongoing deformation around the Dabbahu segment. Most notably, a sequence of new dyke injections began in June 2006 within the rift segment, with the most recent causing a basaltic fissure eruption in August 2007. I will present the latest geodetic observations of deformation at the Dabbahu rift segment, and discuss the implications for the magma plumbing system of the rift. The ongoing pattern of activity at Dabbahu continues to parallel activity during the 1975-1984 Krafla rifting episode (Iceland). We anticipate further dyke injections over the coming years, and continued deformation from relaxation of the lower crust and mantle.


Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry