Tectonic stress state in NE Japan as part of the Okhotsk plate (original) (raw)

An existing geodetic¯ow velocity model, obtained by using an internal free network adjustment technique, is used to derive estimates for various strain rates parameters in NE Japan. The greatest shortening rates of the principal strains, trending ,E±W, are located in regions where much steady, internal, frame-invariant plastic¯ow deformation is observed to be taking place. The internal geodetic adjustment technique yielded the internal deformation in the Tohoku arc; most of the intraplate deformations, including the much folding deformations observed in the inner zone, are produced from within. An interseismic transient elastic loading at a strongly coupled/locked Japan trench would not be needed. The observed ongoing extensive ductile folding deformation in the inner zone of Tohoku may mean that the geodetic strain rates, causing shortening at ,2±3 cm/yr, probably re¯ect the more correct level of the deformation, which is steady/permanent, in NE Japan as compared with seismic/faulting data, which indicate ,0.5 cm/yr shortening.