The big crunch: Physical and chemical expressions of arc/continent collision in the Western Bismarck arc

Abstract

The Western Bismarck arc of Papua New Guinea provides a unique setting in which to study both the seismic and chemical expressions of arc-continent collisional processes. Here collision has been oblique, occurring progressively along the arc from west to east, and currently centred around ∼ 148°E. This progressive collision is reflected in sub-lithospheric seismic activity. Centroid Moment Tensor (CMT) focal mechanism data show that the north-dipping Solomon Sea slab subducting beneath New Britain can be traced westwards beneath the collision front. Beneath the Finisterre Ranges it defines an inverted "U"-shape with a steep northern limb extending to at least 250 km depth. Mechanical decoupl..