D Gravity Inversion for Oceanic Lithosphere in the Okinawa Trough

In this paper, the satellite altimetry gravity data is used to recover the 3D distribution of oceanic lithosphere density in the Okinawa Trough. The oceanic lithosphere is divided into a set of prism cells, each having its own density value. Solutions are obtained by minimizing a global objective function composed of the model objective function and data misfit. The kernel matrix requires large amount of CPU time and computer memory. In inversion function, Wavelet compression method is applied to reduce the CPU time. The 3D gravity inversion result and seismology CMT data are both used to explain the oceanic lithosphere structure in the Okinawa Trough and its neighbor region. The inversion result illustrates high density anomaly under the Okinawa Trough. Considering seismology CMT data, we believe that high density anomaly is related to the convergence between the Philippine plate and the Asian plate. The Philippine plate subducts beneath the Okinawa Trough, which result in the upwelling of mantel material and decrease of the crust thickness. Affected by small scale mantle convections, the continental lithosphere is separated, which result in the spreading of back-arc basin and the formation of the Okinawa Trough.