3-D Gravity Modeling of Subduction Zone around the Japanese Islands

Abstract:

We analyzed satellite gravity data to construct a 3-D crustal density model for the Japanese islands. The aim is to figure out the entire lithospheric structures around the Japanese Islands. The inversion process was constrained by the available previous receiver functions analysis, 3-D results of seismic tomography, and geological data. The nonlinear inversion process is based on the modified Bott’s method and Tikhonov regularization. The inversion results were controlled by three hyper-parameters: the regularization parameter, the anomalous Moho density-contrast, and the reference Moho depth.

The resultant crustal model and Moho relief depths are in good agreement with the previous geological models and the results of seismic studies. The 3-D density model was sliced by three profiles with E-W direction to evaluate the degree of the hypothesis agreement. The preliminary results show that Moho relief depths range from 17 km to 40 km. The small crustal thickness was found in the western Pacific Ocean. The Sea of Japan and the Philippine plate have intermediate-thickness while eastern China and Japanese islands have large crustal thickness. Large crustal thickness can be associated with the subduction of the Pacific Ocean plate, Philippine plate, and Amur plate.