Abstract
THE East Pacific Rise at 12°50' N (Fig. 1) is a fast-spreading ridge with intense hydrothermal activity1, and ophiolite studies2and thermal modelling3 indicate that this is a likely setting for a magma chamber. A recent seismic-reflection experiment4 imaged the top of the magma chamber at this site, at a depth of 1.4 km below the sea floor, and found that it is continuous for tens of kilometres along the rise axis. Here we examine a large set of accurate P-wave travel times from a detailed seismic refraction experiment at the same site5. The patterns observed in the travel times demonstrate that a zone of low seismic velocities exists beneath the rise axis throughout the region studied. The best-fitting two-dimensional structure, obtained from linear inversion of the travel times, includes an axial low-velocity zone (magma chamber) only ∼6 km wide, in which velocities are depressed by more than 0.5 km s-1
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Burnett, M., Caress, D. & Orcutt, J. Tomographic image of the magma chamber at 12°50' N on the East Pacific Rise. Nature 339, 206–208 (1989). https://doi.org/10.1038/339206a0
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DOI: https://doi.org/10.1038/339206a0
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