Teleseismic P-Wave Tomography of the New Guinea-Solomon Arc System

A P-wave tomographic traveltime inversion was applied to obtain a new model of seismic velocity anomalies beneath the New Guinea-Solomon arc system (PN-SL). The P-wave traveltime data, obtained from the revised International Seismological Center catalog, were recorded by 82 seismic stations in the PN-SL. Under the constraints of the epicenter distance, magnitude, and the number of stations recorded, 15009 effective P-wave traveltime data were selected from 2011 teleseismic events. The obtained model showed that the Solomon Sea Plate subducted beneath the New Britain Island along the New Britain Trench at an angle of >70° and that the slab can be traced down to a depth of approximately 800 km. Conversely, we cannot observe a high-velocity anomaly exhibited by the subducted Solomon Sea Plate in the deep mantle at the Trobriand Trench, and the slab stopped at a depth of <200 km. The double subduction of the Solomon Sea Plate strongly modified the subduction patterns of the early subducted Pacific and Australian plates in the mantle along the West Melanesian Trench and the Pocklington Trough, respectively. In addition, the subducted Solomon Sea Plate induced the melting of the upper mantle to form a low-velocity anomaly, which provided the deep dynamic source for the expansion of the Bismarck Sea. Based on the joint consideration of the tomography results and a petrological analysis, the low-velocity anomalies beneath the Solomon Sea and Woodlark Basin are closely related to the early subduction of the Pacific and Australian Plates, respectively.