A seismic refraction experiment in the central Banda Sea

Abstract

A seismic refraction experiment in the central Banda Sea is interpreted by using both slope intercept and delay time function methods. The crustal structure is shown to be oceanic, with velocities (4.97, 6.47, 7.18, and 7.97 km/s) typical of oceanic layers 2, 3A, and 3B and the mantle. Individual layer thicknesses va ry systematica lly along the line, though the range of thicknesses observed for layers 2 ( 1.5-2.0 km) and 3A (2.0-3.5 km) falls well within the range observed for normal oceanic crust. Layer 3B is unusually thick (2.5-4.6 km), the result being slightl y greater than normal depths-to Moho of9-IO km below the sea floor. Shear head waves from layers 3A and 3B are identified on two receivers. In both cases, shear wave conversion occurred at the sediment/layer 2 interface. The observed shear wave velocities and intercepts indicate a Poisson's ratio of 0.25-0.28 in layer 3 and ~0.33 in layer 2. These and earlier results from the southern Banda basin indicate that the entire Banda Sea is underlain by oceanic type crust.