Active Structures in the Northeast Marginal Area of Niigata Plain, Central Japan

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In the northeast margin of the Niigata Plain, many active structures are distributed. Author investigated them to clarify the features, especially their activities in the late Quaternary. The results are summarized as follows.1. The Murakami Hills and the Kushigata Mountains which are situated eastern margin of the Niigata Plain have folded and uplifted. But the rate of uplift of them are not equal. The average rate of uplift in the Murakami Hills is 0.1-0.2mm/yr, and that of the Kushigata Mountains, south of the Murakami Hills is 1-2mm/yr.2. At the western foot of the Kushigata Mountains, active reverse faultings have occured with a sense discordant to the uplifting of the Mountains. The vertical slip rate of them are about 0.3-0.5mm/yr.Around the Murakami Hills, there is no active faultings with a such sense.3. The summit level of Mountains and hills are accordant to the rate of uplift.4. In the eastern margin of the Niigata Plain, the active faults have acted with left-lateral sense. This sense is not according to the regional stress field.These facts represent the regional differences of crustal movement along the Shibata-Koide tectonic line which have played the important role for the reduction of Niigata sedimentary basin. And, it is suggested that active faulting in the eastern margin of the Niigata Plain has occured under the secondary stress field.