Topography and gravity across subduction zones

Abstract

Topographic and Free‐air gravimetric profiles across subduction zones show two distinct signatures. Average low topography (−1250 m) and pronounced gravimetric anomalies characterize west‐directed subduction zones. Average elevated topography (1200 m) and smoother gravimetric waves are peculiar to east‐ or northeast‐directed subduction zones. These differences are particularly evident along the Pacific margins, but they persist also along the other subduction zones of the world in the Atlantic, Mediterranean, Himalayas and Indonesia regions. Therefore topography and gravimetry confirm the existence of two separate classes of subduction zones which appear to be independent of the age and nature of the subducting slab. It is suggested that these differences might be linked to the ‘westward’ drift of the lithosphere relative to the underlying upper mantle.