HR: 0830h
AN: S51C-0071    [PDF]
TI: Seismicity of the Northern Main Ethiopian and Southern Red Sea Rifts: EAGLEII
AU: * Keir, D
EM: d.keir@gl.rul.ac.uk
AF: Department of Geology, Royal Holloway University of London, Surrey, Egham, TW20 0EX United Kingdom
AU: Ebinger, C
EM: c.ebinger@gl.rhul.ac.uk
AF: Department of Geology, Royal Holloway University of London, Surrey, Egham, TW20 0EX United Kingdom
AU: Stuart, G
EM: graham@earth.leeds.ac.uk
AF: School of Earth Sciences, University of Leeds, Leeds, LS2 9JT United Kingdom
AU: Daly, E
EM: e.daly@gl.rhul.ac.uk
AF: Department of Geology, Royal Holloway University of London, Surrey, Egham, TW20 0EX United Kingdom
AU: Ayele, A
AF: Department of Geology and Geophysics, Faculty of Science Addis Ababa University, Addis Ababa, 1176 Ethiopia
AB: The northern Main Ethiopian rift (MER) developed within the Paleogene flood basalt province of NE Africa, and forms the youngest arm of the Afar triple junction. High angle, large-offset border faults formed after 12 Ma, providing a linkage between the East African rift system and the southern Red Sea-Gulf of Aden rifts. However, active subsidence migrated to a narrower zone in the central rift by 3.5 Ma. Since 1.8 Ma magmatism and faulting has become more localized to ~20 km-wide, 60 km-long 'magmatic segments' marked by aligned eruptive centers, fissures, and small offset normal faults. Local seismicity in the northern Main Ethiopian rift is studied using data recorded on an array of up to 80 broadband instruments operational during the period Oct 2001 - Feb 2003, thus providing a glimpse of activity within a rift transitional between continental and oceanic in style. Earthquakes are relatively sparse on rift border faults and are of low magnitude ($<$3.5). Activity is concentrated around faults where the northern Main Ethiopian and southern Red Sea rifts link and around Quaternary eruptive magmatic centres within the rift. This seismicity in magmatic segments is mostly as swarms of shallow events that form clusters of concentrated activity in the northern Main Ethiopian rift. Seismicity is less common in the south, a reflection of a difference in the stage of rift evolution.
DE: 7230 Seismicity and seismotectonics
DE: 8109 Continental tectonics--extensional (0905)
DE: 9305 Africa
SC: Seismology [S]
MN: 2003 Fall Meeting