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Detailed seismic analysis of a lateral mantle inhomogeneity

1975; Elsevier BV; Volume: 25; Issue: 3 Linguagem: Inglês

10.1016/0012-821x(75)90256-3

1385-013X

E. R. Kanasewich, P. R. Gutowski,

Seismic Waves and Analysis

Abstract Seismic array evidence from two large aperture arrays is presented for a small lateral inhomogeneity possibly at the base of the mantle under the Island of Hawaii. Phase velocity and azimuthal deviations plotted at the turning points of the rays suggest that this is a cylindrical body with a high-velocity nucleus having a radius of 150 km and a low-velocity penumbra. The anomaly also produces a characteristic amplitude anomaly or a pulse modification which may be diagnostic. The inhomogeneity is observed where rays have traversed near the core/mantle boundary to 400 km above the core, but there are no observational data at present for an extension to the surface, and observational data for other array sites, favorably placed with respect to earthquake sources, are necessary before the location of the inhomogeneity is established unambiguously.