HR: 1330h
AN: T12D-0501    [PDF]
TI: Micro-earthquake seismicity of the Mid-Atlantic ridge at 5$\deg$S: a different style of tectonic extension
AU: * Tilmann, F J
EM: tilmann@esc.cam.ac.uk
AF: University of Cambridge, Bullard Laboratories Madingley Road, Cambridge, CB3 0EZ United Kingdom
AU: Planert, L
EM: lplanert@geomar.de
AF: GEOMAR, Wischofstr. 1-3, Kiel, 24148 Germany
AU: Flueh, E
EM: eflueh@geomar.de
AF: GEOMAR, Wischofstr. 1-3, Kiel, 24148 Germany
AU: Reston, T
EM: treston@geomar.de
AF: GEOMAR, Wischofstr. 1-3, Kiel, 24148 Germany
AU: Weinrebe, W
EM: wweinreb@geomar.de
AF: GEOMAR, Wischofstr. 1-3, Kiel, 24148 Germany
AB: Based on an ocean-bottom micro-earthquake survey of the Mid-Atlantic ridge just south of the 5$\deg$S transform fault/fracture zone, we find seismic activity to be concentrated within the western half of the median valley. The median valley seismic zone is bounded in along-axis direction by the transform faults to the north, and the tip of the axial volcanic ridge to the south. A few scattered events occurred within the inside corner high, on the transform fault, and in the western side wall close to the segment center. Earthquakes reach a maximum depth of 8 km below the median valley floor and appear to be predominantly in the mantle although a few crustal earthquakes also occurred. The presence of earthquakes in the mantle indicates it is not extensively serpentinized. We infer the median valley seismic activity to arise from slip on two parallel low-angle normal faults which dip from the inside corner toward the spreading axis.
DE: 3035 Midocean ridge processes
DE: 7230 Seismicity and seismotectonics
DE: 9325 Atlantic Ocean
SC: Tectonophysics [T]
MN: 2003 Fall Meeting