Transient rift opening in response to multiple dike injections in the Manda Hararo rift (Afar, Ethiopia) imaged by time-dependent elastic inversionof interferometric synthetic aperture radar data

• Published in: Journal of Geophysical Research 2010, Vol.115 (B09)
• Main Authors: Grandin, Raphael, Socquet, A., Doin, M.-P., Jacques, E., de Chabalier, J.-B., King, G. C. P.
• Format: Article
• Language: English
• Subjects: Earth Sciences; Geophysics; Sciences of the Universe
• ISSN: 0148-0227; 2156-2202
• DOI: 10.1029/2009JB006883

Interferometric synthetic aperture radar (InSAR) data spanning the time intervals separating thirteen dike intrusions in the Manda Hararo-Dabbahu rift (Afar, Ethiopia) from 2005 to 2009 show that transient deformation occurs in the inter-diking period. This deformation can be explained by the presence of seven inflating or deflating pressure sources. By combining the data acquired on four different InSAR tracks, through time-dependent elastic models, we are able to track these deformation modes with a time resolution smaller than 1 month. Sustained deflation of a deep magma reservoir at Dabbahu in the 6 months following the main rifting event of 2005, and slow decelerating post-eruptive re-inflation of two shallow magma reservoirs below Dabbahu and Gabho volcanoes, are monitored. A deflation signal of deep origin on the neighboring rift system is also detected, possibly caused by outflow of material from a preexisting reservoir into the deep plate boundary. In contrast, rapidly evolving deformation is observed at the center of the Manda Hararo rift segment. Transient deformation events are monitored in the weeks/months following the diking events, with pulses of localized rift opening after the dike intrusions, followed by an exponential-like decay of opening rate. This signal may be associated with the replenishment of the central magma reservoir involved in feeding the 2005-2009 dikes. Alternatively, the predominantly horizontal mode of deformation suggests an interaction between the response of the lithosphere to tectonic strain accumulation, and the process of hydraulic connectivity within the central magma plumbing system.