The Timor Trough is a modern 'underfilled' foreland basin created by partial subduction of the outer north west continental shelf of Australia beneath Timor Island in the Outer Banda Arc of eastern Indonesia during the Cenozoic. A change of the effective elastic thickness (EET) of the continental foreland lithosphere from ~80¿20 km to ~25 km over a distance of ~300 km explains (1) the high curvature (~10-7 m-1) on the outer Trough wall, (2) the low shelf forebulge (~200 m) as measured along a reference base Pliocene unconformity, and (3) observed gravity. An inelastically yielding quartzite--quartz-diorite--dunite continental rheology can explain the EET gradient. New, shallow crustal (<8 km), seismic reflection images indicate that Jurassic basement normal faults are reactivated during bending of the foreland. ¿ 1998 American Geophysical Union