abstract

High attenuation of short-period body waves and extremely low surface-wave group velocities have been found for seismic paths that traverse the crust and upper mantle beneath the concave side of the Lesser Antilles island arc (eastern Caribbean). The observations can be explained in terms of the currently accepted models of lithospheric plate subduction at other island arcs such as Fiji-Tonga, Marianas and the Aegean, a characteristic of which is the existence of an abnormally low Q zone in the crust and upper mantle above the down-going slab. The Greater Antilles island arc appears to be tectonically distinct, as subduction is not evident there and no anomalous low-Q zone exists south of Puerto Rico and Hispaniola. The Aves swell is probably not related tectonically to the low-Q zone, or to the subduction process, at least presently.

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