Seismic tomography based on P-wave travel times and improved earthquake locations provides further evidence for mantle-wide convective flow. The use of body waves makes it possible to resolve long, narrow structures in the lower mantle some of which can be followed to sites of present-day plate convergence at the Earth's surface. The transition from subduction-related linear structures in the mid-mantle to long-wavelength heterogeneity near the core-mantle boundary remains enigmatic, but at least some slab segments seem to sink to the bottom of the mantle.

Tomographic imaging reveals seismic anomalies beneath the Sunda island arc, Indonesia, that suggest that the lithospheric slab penetrates to a depth of at least 1500 kilometers. The Sunda slab forms the eastern end of a deep anomaly associated with the past subduction of the plate underlying the Mesozoic Tethys Ocean. In accord with previous studies, the lithospheric slab was imaged as a continuous feature from the surface to the lower mantle below Java, with a local deflection where the slab continues into the lower mantle. The deep slab seems to be detached from the upper mantle slab beneath Sumatra. This complex slab structure is related to the Tertiary evolution of southeastern Asia and the Indian Ocean region.

Summary. We investigated mantle structure beneath the Indonesian region by means of tomographic inversions of traveltime residuals of direct P and the surface-