Changes in Seismic Anisotropy Shed Light on the Nature of the Gutenberg Discontinuity

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Caroline Beghein , Kaiqing Yuan, Nicholas Schmerr, Zheng Xing


The boundary between the lithosphere and asthenosphere is associated with a plate-wide high seismic velocity “lid” overlying lowered velocities, consistent with thermal models. Seismic body waves also intermittently detect a sharp velocity reduction at similar depths, the Gutenberg (G) discontinuity, which cannot be explained by temperature alone. We compared an anisotropic tomography model with detections of the G to evaluate their context and relation to the lithosphere-asthenosphere boundary (LAB). We find that the G is primarily associated with vertical changes in azimuthal anisotropy and lies above a thermally controlled LAB, implying the two are not equivalent interfaces. The origin of the G is a result of frozen-in lithospheric structures, regional compositional variations of the mantle, or dynamically perturbed LAB.



Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics


Surface waves, Seismic tomography, Seismic anisotropy, Oceanic LAB


Published: 2017-11-03 13:02


Academic Free License (AFL) 3.0

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