Structural features in the mid-southern section of the Kyushu–Palau Ridge based on satellite altimetry gravity anomaly

The Kyushu–Palau Ridge(KPR), an anti-S-shaped submarine highland at the center of the Philippine Sea Plate(PSP), is considered the residual arc of the Izu–Bonin–Mariana Island Arc, which retains key information about the cessation of the Western Philippine Basin(WPB) expansion and the Parece Vela Basin(PVB) breakup. Herein,using the new generation of satellite altimetry gravity data, high-precision seafloor topography data, and newly acquired ship-borne gravity data, the topographic and gravity characteristics of the KPR mid-southern section and adjacent region are depicted. The distribution characteristics of the faults were delineated using the normalized vertical derivative–total horizontal derivative method(NVDR-THDR) and the minimum curvature potential field separation method. The Moho depth and crustal thickness were inverted using the rapid inversion method for a double-interface model with depth constraints.
Based on these results, the crust structure features in the KPR mid-southern section, and the “triangular” structure geological significance where the KPR and Central Basin Rift(CBR) of the WPB intersect are interpreted. The KPR crustal thickness is approximately 6–16 km, with a distinct discontinuity that is slightly thicker than the normal oceanic crust. The KPR mid-southern section crust structure was divided into four segments(S1–S4) from north to south, formed by the CBR eastward extension joint action and clockwise rotation of the PVB expansion axis and the Mindanao fault zone blocking effect.