HR: 0830h
AN: S51C-0066    [PDF]
TI: Along-Axis Segmentation of the Main Ethiopian rift from Tomographic Inversion of Local Earthquakes and Controlled Sources: EAGLEII
AU: * Daly, E
EM: e.daly@gl.rhul.ac.uk
AF: Royal Holloway, U of London, Department of Geology, Egham, TW20 0EX United Kingdom
AU: Stuart, G W
EM: graham@earth.leeds.ac.uk
AF: University of Leeds, School of Earth Sciences, Leeds, LS2 9JT United Kingdom
AU: Ebinger, C J
EM: cindy@gl.rhul.ac.uk
AF: Royal Holloway, U of London, Department of Geology, Egham, TW20 0EX United Kingdom
AU: Keir, D
EM: d.keir@gl.rhul.ac.uk
AF: Royal Holloway, U of London, Department of Geology, Egham, TW20 0EX United Kingdom
AU: Ayele, A
EM: observatory.aau@telecom.net.et
AF: Addis Ababa University, PO Box 1176, Addis Ababa, NIL Ethiopia
AU: Waltham, D
EM: d.waltham@gl.rhul.ac.uk
AF: Royal Holloway, U of London, Department of Geology, Egham, TW20 0EX United Kingdom
AB: Geophysical, structural, and geochemical data indicate that the East African rift system in Ethiopia is in a stage of development transitional between continental and oceanic spreading. In the northern Main Ethiopian rift (MER) the archetypal continental rift stage border fault systems bounding the asymmetric rift basins formed at approx 11 Ma. After 3.5 Ma, strain localised to fault systems within the central rift. By 1.8 Ma, faulting and magmatism localised to an en echelon series of 20 km-wide zone, 50-60 km-long `magmatic segments' comprising felsic shield volcanoes and basaltic fissural flows and dikes. As part of the international EAGLE project, 50 broadband Guralp 6TD seismometers were deployed across 3 magmatic segments, and a sector of the rift without magmatic segments. These instruments are nested within the Leeds University broadband array, and the combined net of 80 instruments was used to locate local and regional events (Keir et al., this session). Velocity information was provided by across and along-axis refraction profiles (Mackenzie et al., this session; Keller et al., this session). Over 600 local events, plus 19 controlled explosive sources from EAGLE III provide good ray coverage, with higher resolution in the more seismically active northern sectors of the MER. We present P-wave velocity models of the variations in crustal structure corresponding to rift sectors with and without magmatic segments.
DE: 8109 Continental tectonics--extensional (0905)
DE: 8145 Physics of magma and magma bodies
DE: 8180 Tomography
SC: Seismology [S]
MN: 2003 Fall Meeting