The Crustal Thickness of the Philippine Sea Plate Derived from Gravity Data

Abstract

We constructed a new free-air gravity anomaly map of the Philippine Sea Plate (PSP) using ship-tracked gravity data from the National Geophysical Data Center (NGDC). Our results show that the isogals trend correlates well with the tectonic structures in the PSP. After removing the gravity induced by sea water from the free-air gravity data, we obtained the regional Bouguer gravity anomaly, which is later used to compute the Moho geometry in the PSP by applying the Parker-Oldenburg iterative method. Our results indicate that in the southern part of the West Philippine Basin (WPB) the crustal thickness is nearly homogeneous with a value of about 5 km, which implies that the WPB is quite stable. The low-amplitude and near-zero free-air gravity anomalies clearly indicate that the whole WPB, except at trenches and island arcs, is nearly in a state of isostatic equilibrium. The average crustal thickness of the Palau Kyushu Ridge (PKR) is more than 10 km. In the eastern PSP the crustal thickness gradually increases eastward. Our results also imply that a relatively thin and low density mantle exists beneath the Parece Vela Basin (PVB) as a consequence of back-arc spreading and serpentinized upwells of the thin crustal thickness.

Philippine Sea and East Asian plate tectonics since 52 Ma constrained by new subducted slab reconstruction methods

“…The proximity of the Caroline hot spot at the time of formation of the Caroline plate is consistent with its abnormally thick crust, which is typical of ridge‐hot spot interaction [ Whittaker et al , ]. Crustal thicknesses are 10 to 25 km estimated from gravity, bathymetry, and seismic refraction, in contrast with the basins of the Philippine Sea plate of similar age which are deeper and have estimated crustal thicknesses of ~5 km [ Altis , ; Den et al , ; Yen et al , ]. The only basinal areas of similar crustal thickness in the Philippine Sea Plate are parts of the Benham Rise hot spot track and the region NE of the Palau basin (Figures and ).…”