Gravity Effect of Downgoing Lithospheric Slabs beneath Island Arcs

Recent geophysical data from the northwestern Pacific suggest that the total gravity effect of a downgoing slab beneath island arcs is small and limited in extent to the region of the island arc and trench. The total effect is small either because the density contrast associated with the downgoing slab is small or because the slab is in some manner compensated. The small total effect suggests that it is not possible to obtain details of the configuration of the slab from gravity data alone. The small total effect also suggests that the large positive gravity anomaly associated with some island arcs from satellite data must originate from sources other than the downgoing slab.