Rob L. Evans, Spahr C. Webb, and the RIFT-UMC Team, Crustal resistivity structure at 9 50'N on the East Pacific Rise: Results
of an electromagnetic survey, Geophys Res Letts, vol 29, 2002
We report the first results of an extensive electromagnetic
survey of the East Pacific Rise (EPR) at 9 50'N which used the
magnetometric resistivity (MMR)technique to measure the electrical
resistivity structure of the seafloor in the vicinity of the spreading
center. Ten seafloor magnetometers were deployed in areas of known
hydrothermal activity, in axial sites devoid of venting, and further
off-axis to a distance of approximately 4 km. Data collected at offaxis
sites show higher seafloor resistivities than at axial sites. This
response is opposite to that expected from porosity controlled
resistivity structure, with a thicker high-porosity extrusive layer 2A
off-axis, as required by seismic data. An explanation for the reduced
axial resistivities is that the uppermost few hundred meters of crust
are much hotter beneath the ridge crest than a few kilometers off-axis,
lowering the pore-fluid resistivity.
FILE » 2001GL014106_7966.pdf
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