Abstract Seismic refraction and reflection profiles were recorded on the continental shelf and slope north of Australia and in the Timor-Tanimbar-Aru Trough system of the Banda Sea. This trough system, not deeper than 3.6 km, is the eastern extension of the Java Trench. Morphologically, the area is similar to other circum-Pacific subduction zones, although continental crust, rather than oceanic crust, is being thrust under a series of emergent islands consisting of non-volcanic imbricated crustal blocks. The refraction results reveal a close similarity between the crust underlying the continental shelf and that under the trough system. Typical continental crustal thicknesses (up to 40 km) and velocities were observed. Reflection profiles reveal that the continental slope was formed by predominantly normal faulting and active subsidence, presumably related to the downwarping of the continental shelf into the subduction zone. A tectonic front at the landward (northern) wall of the trough system compressionally deforms unlithified sediments. Uplifting of small crustal blocks into the imbricated island trend is also apparent. The data strongly support the idea that the Timor-Tanimbar-Aru Trough system is the surface trace of a subduction zone.