| Summary: | New and pre-existing seismological data are used to study the neotectonics and the state of stress in the seismic zones of eastern Papua New Guinea and the western Solomon Sea regions. Earthquake hypocentres for the period 1964-90 were relocated, using the Joint Hypocentre Determination (JHD) technique. It is shown that the T axes of earthquakes in the 100-250 km depth range beneath eastern Papau New Guinea are aligned parallel to the seismic zone, with no seismicity below ~250 km. This intermediate-depth seismic zone forms an inverted U-shaped zone, with limbs dipping to the north and south, and is interpreted to be seismicity along the subducted Solomon Sea plate. The northern and southern limbs of the seismic zone are connected by a flattened zone of seismicity which is marked by predominantly strike-slip, and a few normal, fault mechanisms. It is suggested that the Solomon Sea plate at depth beneath the Finisterre mountains is no longer influenced by the tectonic forces acting at the surface, but breaking up and sinking under its own gravitational forces. -from Authors
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