活断層研究
Online ISSN : 2186-5337
Print ISSN : 0918-1024
ISSN-L : 0918-1024
2013 巻 , 38 号
選択された号の論文の5件中1~5を表示しています
論説
  • 木村 治夫, 中西 利典, 丸山 正, 安藤 亮輔, 堀川 晴央
    原稿種別: 論説
    2013 年 2013 巻 38 号 p. 1-16
    発行日: 2013/03/31
    公開日: 2016/03/30
    ジャーナル フリー
    The Itoigawa-Shizuoka tectonic line (ISTL), which is located between the NE and SW Japan arcs, is one of the most major tectonic lines in Japan. The N-S trending Kamishiro fault located in the northern part of the ISTL active fault system is an east dipping reverse fault. Near the southern part of the fault, the alluvial fan formed by a river flowing toward the southeast is tilted to the west by faulting. To reveal shallow subsurface deformation structure above a depth of 5 m, we carried out ground penetrating radar (GPR) profiling along two survey lines, whose lengths are 50 m and 130 m, respectively, across the fault. The GPR data was collected by common-offset modes using the control unit SIR-3000 (Geophysical Survey System Inc.) and the 200 MHz antenna Model-5106(Geophysical Survey System Inc.), and the station spacing was 0.01 m. The depth converted GPR sections after careful data processing are very concordant with the geological section based on drilling and trenching surveys conducted near the GPR survey. The GPR sections show deformation structure of the fan deposits in detail. The vertical displacement of the top of the fan gravel deformed by the Kamishiro fault is over 3.0 m during the last faulting event.
短報
  • 楮原 京子, 黒澤 英樹, 小坂 英輝, 三輪 敦志, 今泉 俊文
    原稿種別: 短報
    2013 年 2013 巻 38 号 p. 17-28
    発行日: 2013/03/31
    公開日: 2016/03/30
    ジャーナル フリー
    The Kuromatsunai Lowland fault zone is a 32 km-long, reverse fault zone which develops through the Kuromatsunai Lowland, southwest Hokkaido. This is a complexed fault zone consists of a series of reverse faults trending approximately north–south. Individual faults are 3-4 km and displace middle to late Quaternary terrace surfaces and deposit, the west side raising up. We observed a fault outcrop of one of the reverse faults in the Kuromatsunai Lowland. The outcrop on the Babasawa River exposes Lower Pleistocene sediments that are thrusting over the youngest sediment along the F1 fault. Tephra analyses and radiocarbon dates indicate at least two seismic events. One is between 10 C and 17 C AD, and another is about 20 ka. The younger event is not associated with any of the known paleoseismic events from the Warabitai fault in south. Therefore, the F1 fault and Warabitai fault did not move simultaneously. The layer III of the Late Glacial age is displaced vertically 1.6 m by the F1 fault yielding the vertical component of net slip to be about 0.08 mm/yr.
  • 水本 匡起, 田力 正好, 松田 時彦, 松浦 律子
    原稿種別: 短報
    2013 年 2013 巻 38 号 p. 29-40
    発行日: 2013/03/31
    公開日: 2016/03/30
    ジャーナル フリー
    The western margin of the Fukushima basin is bounded by active faults, that extend from north to south about 57 km in length. The Fukushima basin has been subdivided into northern and southern parts based on differences in morphology of tectonic landforms, horizontal geometry of the fault traces and subsurface fault structures in each part by previous studies. We focused on horizontal geometry of fault traces around Iizaka Town, which is located between the northern and southern parts of the basin, where fault traces seem bent. The northeast-trending Kori fault defines the western margin of the northern part of the basin. At the southern end of the Kori fault, fault traces were newly identified for 2 km long on the south in the basin area. Fault-related landforms were detected as fault scarps in Pleistocene to Holocene terrace surfaces. The Daiyama fault also extends from northeast to southwest in the western margin of the southern part of the basin. The northern end of the Daiyama fault is composed of several en-echelon faults. The Kori fault overlaps with the Daiyama fault for about 2 km long at Iizaka Town. An east-trending fault trace, Iizaka fault, was mapped by previous studies between the two faults. Numerous landslides are distributed in the mountains north of the Iizaka area, where we inferred existence of an old large-scale landslide. This landslide is eroded by small streams flowing to the south to form fluvial terraces, and is partly covered by recent landslide deposits. Scarps and tilting of fluvial terraces which were previously mapped as tectonic landforms in this area were probably formed due to gravitational movement of this old landslide deposit. No evidence for Holocene surface faulting can be found along the previously-reported Iizaka fault. Thus, the northern and southern parts of the western marginal fault zone of the Fukushima basin are probably not connected by the east-trending Iizaka fault, but separated by a 4 km wide stepover, in the central part of the basin.
  • 森野 道夫, 金子 史夫, 松尾 淳
    原稿種別: 短報
    2013 年 2013 巻 38 号 p. 41-49
    発行日: 2013/03/31
    公開日: 2016/03/30
    ジャーナル フリー
    The Yerevan fault is an inferred active blind fault that extends along the northeastern margin of the Ararat Basin, although there has been no definitive evidence for its active faulting. The fault is considered as an important structure for the seismic hazard assessment of Armenia, since it extends near Yerevan City, the capital of Armenia. Our tectonic-geomorphic mapping reveals that the Vedi fault, an ~ 3 km-long fault that appears to be branched from the Yerevan fault, is an emergent active structure. The trench investigation and radiocarbon dating at Nor Ughi confirm its recent activity and suggest that the Vedi fault may have ruptured during the AD 893 Dvin earthquake, the epicenter of which is inferred to be on the southeast of Yerevan City. Judging from the geographic relationship between the Vedi and Yerevan faults, it seems likely that the main seismic source of the Dvin earthquake was the Yerevan fault, with the Vedi fault rupture being a minor branched slip.
資料
  • 太田 陽子
    原稿種別: 資料
    2013 年 2013 巻 38 号 p. 51-54
    発行日: 2013/03/31
    公開日: 2016/03/30
    ジャーナル フリー
    “Geological Law”of Taiwan is enacted in Dec. 2010 to improve the geological investigation system, to manage geological information of public land, and to establish basic geological information for natural environmental changes and land resources management. Central Geological Survey is responsible for the nation wide activity and municipal governments are for county/city level. Active fault is not specially mentioned in this main law, but some topics on the active fault are included in the additional rule proclaimed in 2011. This note intends to introduce the Geological Law with some details on active faults.
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