HR: 1330h
AN: V22A-0574    [PDF]
TI: Rapid opening of the Asal rift in Afar observed with radar interferometry
AU: * Peltzer, G
EM: peltzer@ess.ucla.edu
AF: University of California Los Angeles, ESS Dept., 595 Charles Young Dr. East, Los Angeles, CA 90095 United States
AU: * Peltzer, G
EM: peltzer@ess.ucla.edu
AF: Jet Propulsion Laboratory, California Institute of Technology, MS300-233, 4800 Oak Grove Dr., Pasadena, CA 91109 United States
AU: Mignan, A
EM: mignan@ipgp.jussieu.fr
AF: Institut de Physique du Globe, 4 place Jussieu, Paris, 75005 France
AU: King, G
EM: king@ipgp.jussieu.fr
AF: Institut de Physique du Globe, 4 place Jussieu, Paris, 75005 France
AU: Manighetti, I
EM: manig@usc.edu
AF: University of Southern California, Earth Science Dept., 3651 Trousdale Pkwy, Los Angeles, 90089 United States
AB: Located at the western end of the Aden ridge, the Asal rift is the first emerged section of the ridge propagating into Afar and the locus of intense volcanic and seismic activity. We use radar interferometry data acquired by the Canadian satellite Radarsat between 1997 and 2003 from both ascending and descending passes to measure the surface deformation in a 100 km wide region centered on the rift. The turbulent atmosphere in this sub-tropical region produces a phase delay error in the data exceeding the tectonic signal we seek. To estimate the deformation rates from the series of interferograms, we solve a least-square problem and derive the vertical and rift-perpendicular, horizontal components of the surface velocity from the series of ascending and descending line of sight observations by the radar. The resulting 2-component surface velocity map of the rift area shows the following features: A ~40 km wide zone centered on the rift is inflating at a rate of ~7 mm/yr. The ~8 km-wide central rift subsides at a rate of ~2mm/yr with respect to the shoulders of the rifts. The horizontal velocity indicates extension across the central rift at a rate of up to 20 mm/yr, gradually decreasing in the far field, the maxima of the horizontal velocity being located on both side of the rift, ~12 km from its axis. This local opening rate exceeds the 13 mm/yr far-field plate motion between the Arabia and Nubia plates, suggesting that magmatic activity is currently controlling the opening of the Asal rift. Preliminary models shows that a 4 km deep dyke system expanding both laterally and upward accounts for the observed velocity field across the Asal rift.
DE: 8109 Continental tectonics--extensional (0905)
DE: 8123 Dynamics, seismotectonics
DE: 8434 Magma migration
DE: 8494 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting