Tectonic landforms and Quaternary activity along the southern part of the Itoigawa- Shizuoka tectonic line (Hakushu-Nirasaki district), central Japan
Tectonic landforms and Quaternary activity along the southern part of the Itoigawa- Shizuoka tectonic line (Hakushu-Nirasaki district), central Japan
复制标题
日本中部糸鱼川-静冈构造线南部（白州-韭崎地区）的构造地貌和第四纪活动
DOI：
--
复制
发表时间：
2012
期刊：
影响因子：
--
通讯作者：
Masayoshi Tajikara
中科院分区：
文献类型：
--
作者：
Masayoshi Tajikara
丝鱼川-静冈构造线（ISTL）活动断裂系统是日本最长、最复杂的活动断裂系统之一。该系统包括北方、中部和南部部分。在中段和南段边界（白州Nirasaki）附近，调查和绘制了与ISTL活动断层系统有关的构造地貌。经过调查，以下事情变得清楚了。白州断层的垂直滑动速率为0.2-0.4mm/yr，在最南端分叉为两条断层。东断裂为逆断层，西断裂为左旋断层。向川断层由许多短断层组成，活动性低（<0.1mm/yr）。向川断层被认为是下川井断层的最北端。在同一位置，形成了走向E-W的宽挠曲（Mukawa挠曲）。向川挠曲南侧隆起，垂直位移速率为0.6mm/yr。据估计，向川断层容纳了向川挠曲的一部分位移。由于白州断层的分支端和下川井断层的分支端彼此相对，因此假定此处存在分段边界。根据阶地面的位移，后欧赞断裂过去一直被认为是一条活动断裂。然而，经过详细的调查，很明显，阶地没有因任何断层而变形。因此，认为后欧赞断裂南段近期活动不大。根据断层的滑动速率、中更新世地层的位移和地下构造的估计，推断断层的活动历史如下：（1）新近纪晚期至第四纪早期，釜石山白州后岳山断层活动。(b)第四纪早中期，活动段从白州后奥山断裂向釜桥川下井断裂跳跃。这些断层抬升了赤石山脉、科马山脉和中山山脉。(c)第四纪晚期，釜志川断层活动减弱，白州断层重新活动。新形成了向川断层（向川挠曲），断层系统的活动区域成为了釜石山白州向川下井断层。这些断层抬升了赤石山脉和科马山。
The Itoigawa-Shizuoka tectonic line (ISTL) active fault system is one of the longest and the most complex active fault systems in Japan. The system comprises the northern, the middle, and the southern segments. In the vicinity of the boundary of the middle and the southern segments (Hakushu Nirasaki), tectonic landform related to the ISTL, active fault system is investigated and mapped. As a result of investigation, the following things became clear. The Hakushu fault, with vertical slip rate of 0.2-0.4mm/yr, branches into two faults in a southernmost part. The eastern fault is reverse fault, and the western one is left lateral fault. Mukawa faults comprise many short faults with low activity (<0.1mm/yr). Mukawa faults are assumed to be a northernmost part of the Shimotsuburai fault. In the same location, broad flexure (Mukawa flexure), trending E-W, is formed. The Mukawa flexure uplifts southern side, with vertical displacement rate of 0.6mm/yr. It is estimated that the Mukawa faults accommodates a part of the displacement of the Mukawa flexure. Since branching end of the Hakushu fault and the Shimotsuburai fault are confronting each other, it is assumed that the segment boundary exists here. The Hououzan fault has been considered to be an active fault formerly, based on the displacement of the terrace surface. As a result of detailed investigation, however, it become clear that the terrace was not deformed by any fault. Therefore, it is thought that the southern part of the Hououzan fault is not active recently. Based on the slip rate of faults, the displacement of the middle Pleistocene strata, and the estimation of subsurface structure, the history of fault activity is inferred as follows: (a) In late Neogene to early Quaternary, the Kamanashiyama Hakushu Hououzan faults were active. (b) In early to middle Quaternary, active segment jumped from the Hakushu Hououzan faults to the Kamanashigawa Shimotsuburai faults. These faulting uplifted the Akaishi Range, the Koma Mountains and the Nakayama. (c) In late Quaternary, the Kamanashigawa fault became inactive, and the Hakushu fault reactivated. The Mukawa faults (Mukawa flexure) were newly formed, and the active region of the fault system became the Kamanashiyama Hakushu Mukawa Shimotsuburai faults. These faulting uplifted the Akaishi Range and Koma Mountains.