HR: 0800h
AN: T41A-0355    [Abstracts]
TI: Continued dyking in the Dabbuhu Rift segment, Afar, Ethiopia, from radar interferometry.
AU: * Hamling, I J
EM: i.hamling@see.leeds.ac.uk
AF: School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, United Kingdom
AU: Keir, D
EM: keir@gl.rhul.ac.uk
AF: School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, United Kingdom
AU: Ayele, A
EM: atalay@geobs.aau.edu.et
AF: Geophysical Observatory, Addis Ababa University, Addis Ababa, POBox 1176, Ethiopia
AU: Calais, E
EM: ecalais@purdue.edu
AF: Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, IN 47907, United States
AU: Ebinger, C
EM: cebinger@earth.rochester.edu
AF: Department of Earth and Environmental Science, University of Rochester, Rochester, NY 14627, United States
AU: Lewi, E
EM: elias_lewi@yahoo.com
AF: Geophysical Observatory, Addis Ababa University, Addis Ababa, POBox 1176, Ethiopia
AU: Yirgu, G
EM: yirgu.g@geol.aau.edu.et
AF: Geophysical Observatory, Addis Ababa University, Addis Ababa, POBox 1176, Ethiopia
AU: Wright, T
EM: t.wright@see.leeds.ac.uk
AF: School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, United Kingdom
AB: The 60-km-long Dabbahu segment of the Nubia-Arabia plate boundary lies in the Northern Ethiopian region of Afar. In September 2005 a major rifting episode resulted in the injection of a 60-km-long dyke with a maximum thickness of ~8m (Wright et al., 2006). Subsidence observed at Dabbahu and Gabho volcanoes implied that some of the magma was sourced from shallow reservoirs beneath the volcanoes. Using a combination of satellite interferometry, GPS and seismicity we aim to monitor the ongoing deformation in the Dabbahu rift segment. Interferograms in the following months show only isolated deformation around the volcanoes and around the centre of the Dabbahu rift segment. However, in June 2006, intense deformation is observed along a rift parallel, 10 km long zone extending north of Ado"Ale, which is a volcanic complex located in the middle of the rift segment. Modelling of radar interferometry (InSAR) data indicates the injection of a ~2 m thick, ~10 km long dyke, with deformation spatially coincident with seismicity (Keir et al., this session). Since June 2006 a further 5 dyke intrusions have been detected using InSAR - in July, September and December of 2006 and in January and August of 2007. Elastic modelling of InSAR data suggests that a ~2 m thick, ~9 km long dyke was intruded in July 2006 followed by a ~2 m thick, ~8 km long dyke in September, neither dyke reached the surface and both dykes were confined to the upper 10 -12 km of the crust. Preliminary results suggest similar styles of intrusion for the December 2006 and January 2007 dykes. A fissural basaltic eruption occurred with the August 2007 deformation showing that the dyke reached the surface. . All dykes since June 2006 are south of the Ado Ale complex - a rifted silicic centre in the middle of the rift segment. InSAR and GPS show no deflation at either of the volcanoes at the northern end of the segment implying an alternate source is feeding the ongoing intrusions. We do not observe surface subsidence associated with any source region, and thus require a deep source (> ~ 8 km) and suggest that this is located near the centre of the rift segment. The apparent migration sequences seen so far appear to be similar to those seen in Iceland during the 1975-1984 Krafla rifting episode, and we anticipate further dyking episodes and eruptions over the next few years.
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 5475 Tectonics (8149)
DE: 6924 Interferometry (1207, 1209, 1242)
DE: 6969 Remote sensing
DE: 8105 Continental margins: divergent (1212, 8124)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting