ESTIMATION OF THE PACIFIC PLATE DEFORMATION

For modeling of Pacific plate motion, intra-plate deformation has barely or never been estimated before. Yet several pieces of evidence of deformations are indicated, mostly for continental plates and less so for the oceanic plates, such as diffuse oceanic plate boundaries (e.g., Gordon, 2000). In the case of paleomagnetic analyses, the shape of an isochron on the Pacific plate does not match the coeval shape of the isochron on the Antarctica plate. This makes modeling of relative motion of the two plates inaccurate. In the case of a yearly scale of deformation of the plates, GNSS data on the continents and islands show patterns of the distributions of expansion and contraction for the oceanic plates.

We analyzed those patterns and will show that the expansions occur near subduction zones and the contractions occur near oceanic ridges on the Pacific plate. The result is quite in harmony with the notion of the slab pull force and the ridge push force. Furthermore, those patterns are correlated with deformations inferred from the paleomagnetic results on the plates. Finally, we tried to construct a model of the absolute plate motion for the Pacific plate including the small deformations and compared the result with the absolute motion of the Pacific plate without any deformation included.