著者

竹村 利夫

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:00167444)

巻号頁・発行日

vol.51, no.9, pp.721-729, 1978-09-01 (Released:2008-12-24)

参考文献数

20

被引用文献数

1 1

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The Takashozu fault system, running NE-SW direction, is located at the northwestern foot of the Takashozu Mountains, Toyama Prefecture, and separates the Tonami Plain from the high mountains. Along the fault line, several kinds of fault topographies have developed, such as terminal facets, kern cols, kern buts and valleys flowing parallel to the strike of the fault. At Inami and Akasobu, the Miocene andesitic rock has thrusted up from south to north onto the terrace gravels of the middle and upper Pleistocene ages. The Takashozu fault has dislocated vertically the several levels of terrace surfaces here and there along the fault line. The higher the terraces are, the larger the amount of displacement is. In the drainage basin of the Sho River, it is inferred that not only Pleistocene terraces but also Holocene terrace gravel beds have been cut by the fault activities. In the southwestern part of the Tonami Plain, the gradient of the terrace surface is steeper in the older terraces. The valley dissecting the higher terrace surfaces shows an asymmetric form, i.e., the valley walls of the northern side are generally steeper than those of the southern side. It would be considered that the principal factor forming this asymmetric valley topography is the continuous upheaval of the mountains located to the south of the plain.

著者

竹村 利夫 藤井 昭二

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.22, no.4, pp.297-312, 1984-02-29 (Released:2009-08-21)

参考文献数

38

被引用文献数

12 10

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There are many active faults in central Japan. Several active faults distributed in the northern part of the Hida mountains are described in detail in this paper.The Atotsugawa, Mozumi and Ushikubi faults, 40-80km in length, are NE-ENE in trend and displaced to the right side. The amounts of horizontal displacement as revealed in the offsets of the streams crossing the fault lines are about 1-3km, and the amounts of vertical displacement are 100-300m with the northwest side upthrown.The Kazura fault, 30km long, is NNW in trend and displaced to the left side. The amount of horizontal displacement is 1km as recognized from the stream offset, and the amount of vertical displacement is 100-200m with the west side upthrown.The Atotsugawa fault has displaced the Pleistocene terraces and lake deposits (20, 000- 40, 000y.B.P.) as much as 50-60m vertically at the outcrops of the Magawa River area located up the Jyoganjigawa River. Also the Holocene terraces (about 500y.B.P.) have been displaced 1-4m vertically. The average vertical displacement rate of the Atotsugawa fault is 1-4m/1000y., and the average lateral displacement rate is 1-5.7m/1000y. as judged from the pitch θ of striation on the fault planes.Several outcrops are found along the Mozumi, Ushikubi and Kazura faults. Late Pleistocene and Holocene terraces have been cut and displaced by faults. The average rate of displacement was 0.4-1.5m/1000y. in vertical displacement. The lateral component of displacements are usually larger than or nearly the same as the vertical components.These faults can be ranked as A class or the upper half of B class in degree of activities.