title: Waveform tomography reveals channeled flow at the base of the oceanic asthenosphere.
abstract: Understanding the relationship between different scales of convection that drive plate motions and hotspot volcanism still eludes geophysicists. Using full-waveform seismic tomography, we imaged a pattern of horizontally elongated bands of low shear velocity, most prominent between 200 and 350 kilometers depth, which extends below the well-developed low-velocity zone. These quasi-periodic fingerlike structures of wavelength ~2000 kilometers align parallel to the direction of absolute plate motion for thousands of kilometers. Below 400 kilometers depth, velocity structure is organized into fewer, undulating but vertically coherent, low-velocity plumelike features, which appear rooted in the lower mantle. This suggests the presence of a dynamic interplay between plate-driven flow in the low-velocity zone and active influx of low-rigidity material from deep mantle sources deflected horizontally beneath the moving top boundary layer.
authors.affiliation: Berkeley Seismological Laboratory, Berkeley, CA 94720, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: French
authors.forename: Vedran
authors.initials: V
authors.lastname: Lekic
authors.forename: Barbara
authors.initials: B
authors.lastname: Romanowicz