Crustal structure and variation along the southern part of the Kyushu-Palau Ridge

As an interoceanic arc, the Kyushu-Palau Ridge (KPR) is an exceptional place to study the subduction process and related magmatism through its interior velocity structure. However, the crustal structure and its nature of the KPR, especially the southern part with limited seismic data, are still in mystery. In order to unveil the crustal structure of the southern part of the KPR, this study uses deep reflection/refraction seismic data recorded by 24 ocean bottom seismometers to reconstruct a detailed P-wave velocity model along the ridge. Results show strong along-ridge variations either on the crustal velocity or the thickness of the KPR. P-wave velocity model is featured with (1) a crustal thickness between 6–12 km, with velocity increases from 4.0 km/s to 7.0 km/s from top to bottom; (2) high gradient (∼1 s −1 ) in the upper crust but low one (