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Slip-partitioning on the Itoigawa-Shizuoka Tectonic Line, central Japan

日本中部糸鱼川-静冈构造线上的滑移分区

基本信息

批准号：
11480019
负责人：
IKEDA Yasutaka
金额：
$ 9.41万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

The overall objective of this study is to clarify the partitioning of slip on low-angle, oblique-slip faults. The test field is the central and northern part of the Itoigawa-Shizuoka Tectonic Line(ISTL), central Japan. The following results are obtained :(1)High resolution S-wave seismic reflection profiling across the Kamishiro fault(northern part of ISTL)revealed that the fault sprays up-dip into several fault planes, the lowest of which is a blind thrust at a depth of 50-60 meters.Radiocarbon dating of deformed sediments indicates that the rate of net slip on the Kamishiro fault is about 6 mm/yr, which value is significantly larger than previous estimates without considering fault spraying(2)P-wave and S-wave seismic reflection profiling was carried out across the central part of ISTL at Fujimi. The P-wave profile revealed that a high-angle, East-dipping fault is developed on the hanging-wall side of a low-angle, west-dipping fault. Late Quaternary surface deformation indicates that the former is dominantly strike-slip, whereas the latter is dominantly thrust. Bouguer gravity anomalies suggest that the low-angle thrust is the material boundary between Quaternary-Pliocene sediments on the east and Miocene and older rocks of Akaishi range on the west. These lines of evidence indicates that oblique slip(thrust+left slip)on the deeper part of ISTL is partitioned at shallow depths into two fault planes ; the strike-slip component is accommodated on the high angle fault that develops in the low-angle thrust sheet.(3)Similar phenomenon is observed in the northern part of ISTL at Matumoto and Shiojiri, although the master fault(material boundary)here is not west-dipping but east-dipping.

本研究的总体目标是阐明低角度，顺滑断层的滑动分区。试验场位于日本中部的Itoigawa-Shizuoka构造线（ISTL）的中部和北方。（1）通过对上代断层（ISTL的北方部分）的高分辨率S波地震反射剖面测量，发现该断层向上倾斜形成多个断层面，其中最低的一个断层面为50-60 m深的盲冲断层，变形沉积物的放射性碳测年结果表明，上代断层的净滑动速率约为6 mm/年，这一数值明显大于以前不考虑断层喷射的估计值。（2）在藤见的ISTL中部进行了P波和S波地震反射剖面测量。P波剖面显示，在低角度西倾断层的上盘一侧，发育一条高角度东倾断层。晚第四纪地表变形表明前者以走滑为主，后者以逆冲为主。布格重力异常表明，低角度逆冲断层是东部上第三纪-上新世沉积物与西部中新世和更古老的赤石山脉岩石之间的物质边界。这些证据表明，在ISTL的较深部分的斜滑（逆冲+左滑）被划分为两个断层面在较浅的深度;走滑分量被容纳在高角度的故障，在低角度的逆冲席发展。（3）在松本和盐尻的ISTL的北方部分也观察到类似的现象，尽管这里的主断层（物质边界）不是西倾的而是东倾的。