Landward migration of active folding based on topographic development of folds along the eastern margin of the Japan Sea, northeast Japan

The eastern margin of the Japan Sea, northeast Japan, lies in a strongly compressional area, and contractional deformation in the region is ongoing. We reconstructed the temporal and spatial evolution of contractional deformation across the Tohoku district on the eastern margin of the Japan Sea, by using surface geologic and geomorphologic data. We measured the distance from the fold hinge to the topographic ridge line in antiforms, developed by surface uplift, associated with fold growth under the E-W to WNW-ESE compressional stress regime. The topographic development of fold structures, developed in the region since the Pliocene, is consistent with the activity of the folds. When the folding that generates the uplift becomes inactive, the topographic contrasts between hinge and ridge location can be remarkable. Spatial variations in this parameter are consistent with the systematic eastward migration of fold growth in the area. The documentation of fold-related topography thus provides important information for understanding the dynamics of folding along the eastern margin of the Japan Sea.