Abstract
The Kakuda Massif and the Mineoka Hill are situated in the Western Margin of the Echigo Plain, where underlain by the Miocene volcanic rocks and the Plio-Pleistocene sediments. The Mineoka Hill are isolated from the foot of the Kakuda Massif by low lands. The Echigo Plain Western Fault Zone runs around there, so it is feared that next big earthquakes will surely occur. The compilation of the geotectonic history in the Mineoka Hill leads to the activated history of its fault zone. It would suggest us to consider the next quakes. The geotectonic history in the study area is as follows.
Takenomachi Stage (Plio-Early Pleistocene): Shallow to bathyal sea environment. Fusube-Tojima Stage (Middle-Latest Pleistocene, 145±40 ka): Uplifting of the Kakuda Massif generated the Echigo Plain Western Fault Zone and the Mineoka Hill. Nika Stage (Earliest-Late Pleistocene, 106±39 ka): Continuity of the uplifting of the Kakuda Massif and the block faulting at the Mineoka Hill. Shallow sea to delta environment. Post-Nika Stage (Late Pleistocene to Recent): Powerful uplifting of the Kakuda Massif formed the “Mineoka Isolated Hill” and the Echigo Plain Western Fault Zone.
