Present and past regional ridge segmentation: Evidence in Geoid data

Global geoid data from the Geosat altimeter satellite and topography data have been analysed in the Pacific and Atlantic oceans to study present (along-axis) and past (off-axis) regional mid-ocean ridge segmentation. Along the Mid-Atlantic Ridge, East Pacific Rise and Pacific-Antarctic Ridge, axial geoid and depth variations are positively correlated at length scale 800–1000 km. Respective peak to peak amplitudes are in the range of 0.4–0.8 m and 200–400 m. Axial variations are correlated with the position of large offset transform faults which coincide with geoid and topography lows. Triple junctions are also located in geoid and topography lows. The observed admittance between geoid and depth is estimated to 2 ± 0.5 m/km, a value indicative of a dynamic (convective) origin for the along-axis regional variability. Off-axis analysis shows a regional pattern of geoid (topography) anomalies elongated in the direction of spreading. This pattern has also a length scale of 800–1000 km and possibly represents past regional segmentation. Large offset fracture zones coincide with off-axis geoid (topography) lows.

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