東北本州弧における後期新生界の変形度について  [in Japanese] Degree of deformation of late Cenozoic strata in the Northeast Honshu Arc  [in Japanese]

Horizontal shortening ratios of the late Cenozoic strata in the Northeast Honshu Arc are calculated from geological cross sections. Shortening ratios show small values (less than 2%) in the outer belt of northeast Honshu and increase remarkably across the Quaternary volcanic front. In the inner belt, the average values of shortening ratios are 4-7% and highly deformed zones, showing more than 20% shortening, lie along the Japan Sea coast, the average shortening ratios across the Northeast Honshu Arc show a maxirnum value (8% shortening) in the northern part of Honshu and gradually decrease towards the north and south along the arc. The average shortening ratios of western Hokkaido are 4-5%, smaller than those of the southern part of northeast Honshu. The average strain rates of shortening in the central part of northeast Honshu are on the order of 10^<-8>/year and much greater than that estimated from Quaternary fault data.