東北本州背弧南部における後期新生代の褶曲機構と地殻変動  [in Japanese] Late Cenozoic folding mechanism and crustal dynamics in the southern back arc area of Northeast Honshu, Japan  [in Japanese]

Late Cenozoic crustal movement in the back arc area of Northeast Honshu is analyzed based on the structural characteristics of folding process of the Plio-Pleistocene system in central Niigata Prefecture in addition to the "contradictory" tilted granitic mountain blocks in northern Niigata Prefecture. As a result, we come to the conclusion as follows: 1. A differential uplifting in the inland area of Northeast Honshu initiated at the late Pliocene, and has been intermittently acting and acceleratively intensified during the late to the latest Pliocene to form the recent style of mountain topography. This uplifting might becaused by the mutual relation of the crustal dynamics in the back arc area to that in the fore arc one. 2. The tectonic stress field that folded the Plio-Pleistocene system was that of horizontal compression oriented NW-SE or E-W at the early stage, and it changed to the vertical compressive one at the later stage. This can be interpreted that the stress field originated and gradually intensified by the upheaval of the basement surpassed the lateral compressive stress field continuing from the early stage. 3. A listric fault system was formed in the northern part of the Niigata Prefecture along the eastern margin of the Sea of Japan during the middle to the latest Pleistocene at the same time as the above-mentioned block movement, This fault system can elucidate the formation of the "contradictory" tilted blocks with topographically westward and geologically eastward sense of tilting. This suggests that the spreading mechanism of the Sea of Japan changed from the "active rifting" at the early stage to the "passive rifting" at the later stage at least in part. 4. A close relationship between the spreading of the Sea of Japan from the west to the east and the crustal movement of the fore arc are a must be taken into consideration. When the compresssion from the Pacific side is dominant, the back arc area will be under the compressive state, and vice versa. The crustal dynamics of the back arc area of Northeast Honshu might have been depending upon the lateral compressive-tensile movement acting on this region in the Japanese Islands.