Structural evidence for large‐scale top‐to‐the‐north normal displacement along the Median Tectonic Line in southwest Japan

Abstract

Abstract The Median Tectonic Line (MTL) is a first‐order tectonic boundary that separates the Sanbagawa and Ryoke Metamorphic Belts. Strike‐slip movements on the MTL have been well documented by many workers. New field based structural studies in the Sanbagawa Belt close to the MTL reveal a large number of secondary faults and semibrittle shear bands indicating a top‐to‐the‐north normal sense of displacement. The strikes of these shear zones and their spatial distributions suggest that development of these structures is related to movements on the MTL. These results imply that the MTL has a large‐scale normal shear component on a regional scale that can help account for the exhumation of the Sanbagawa Belt. Our proposed history of the MTL can also account for changes in the geometry of folds in the Sanbagawa Belt.