HR: 0800h
AN: GP11A-0817    [Abstracts]
TI: Electrical Conductivity Across the Northern Ethiopian Rift
AU: Hautot, S
EM: hautot@univ-brest.fr
AF: IUEM-UBO UMR Domaines Oceaniques, Place Nicolas Copernic, Plouzane, 29280 France
AU: * Whaler, K A
EM: kathy.whaler@ed.ac.uk
AF: School of Geosciences The University of Edinburgh, Grant Institute West Mains Road, Edinburgh, EH3 9JW United Kingdom
AB: Audio-frequency magnetotelluric data were acquired along an approximately 200km long profile across the northern Ethiopian rift in early 2003. We present examples of the data collected, discuss their dimensionality, and show a two-dimensional model along the profile. The model has high conductivity close to the surface beneath the rift where there is volcanic activity and partial melt, as expected, but also in a mid-crustal layer on the northern side of the plateau. A sensitivity analysis demonstrates that this layer is required, and that there is a difference in plateau structure on the two sides of the rift (which are on different plates). There is no northern plateau mid-crustal layer corresponding to our conductor on seismic refraction and wide angle reflection data along the same profile, but they do also show a difference in structure on the two sides of the rift. The last volcanism on the northern plateau where our mid-crustal conductor is strongest was ~11 Ma when the mid-Ethiopian rift propagated north, but close to the rift, where we do not see a mid-crustal conductor, there was volcanism only 2 Ma. Thus although volcanism is the most likely explanation for our mid-crustal conductor, interpretation is not straight-forward.
DE: 9305 Africa
DE: 8110 Continental tectonics--general (0905)
DE: 3210 Modeling
DE: 0925 Magnetic and electrical methods
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting