西南日本の3次元深部構造と広域重力異常

抄録

The regional gravity anomalies were calculated in Southwestern Japan presuming a three-dimensional density structure. The gravitational effect was calculated by the structural model represented by aggregate bodies of triangular vertical prisms which was generated by compiling the existing vast amount of data on the depths of lower surface of the crust and upper surface of the plate slab in this region. The densities of the Pacific and Philippine Sea plate slabs, upper and lower crusts and asthenosphere were presumed referring to past research. It was shown by the calculation that the gravitational effect of the crust has larger amplitude than that of the plate slabs in this region, while variation of the presumptive density of the plate slab is more effective than that of the crust. Comparison of the regional gravity correction by means of the above method with the ones by the spatial filtering method and the least square method shows that the former derives more accurate local gravity anomaly than the latter. The regional gravity anomaly can be calculated by the above method at an arbitrary point in Southwestern Japan, and then more accurate regional gravity correction can be performed for the analysis of local gravity structure.