Large arrows indicate general plate motion directions.
The Manus Basin occupies a backarc position relative to present-day subduction on the New Britain Trench to its south. Creation of new oceanic crust occurs at the Manus spreading center and at smaller segments to its west. Major transform faults are somewhat oblique to the spreading segments. The eastern Manus rift zone is a pull-apart structure between two of the major transform faults. It is underlain by thinned lower Tertiary arc crust, equivalent to exposures on New Ireland to the north and New Britain to the south.