抄録
Crustal strain field in the Northeastern Japan Arc has been revealed by repeated geodetic surveys. The crustal strain field is divided into four tectonic provinces, that is, the Kitakami Mountains Area (outer arc), the Uetsu Area (inner arc), the Honjo-Matsushima Tectonic Zone and the southern part of the Northeastern Japan Arc. These strain provinces relate closely to the geophysical and the geological phenomena in their provinces. The extentional strain field in the Kitakami Mountains Area shows that the compressional stress which is caused by the subduction of the Pacific Plate has not conveyed beyond the aseismic front. It is considered that the extentional strain field in the Kitakami Mountains Area is related to the continuous uplift phenomena of the Kitakami Mountains Area since the middle Miocene. The E-W compressional strain field in the Uetsu Area agrees with the folding zone which shows the E-W crustal shortening, and supports a new idea that the Eastern Japan Sea Margin is a plate boundary between the Eurasian and the North American Plates. The strains in the Honjo-Matsushima Tectonic Zone are small. It is considered from the geophysical and the geological data that the Honjo-Matsushima Tectonic Zone is a deep crustal fracture zone which divides the Northeastern Japan Arc into the northern and the southern blocks.
