Holocene Faulting of the Shigenobu Fault, the Median Tectonic Line Active Fault System, West Shikoku, Japan

• GOTO Hideaki

  Research Fellow of the Japan Society for the Promotion of Science, Graduate Student, Hiroshima University

• NAKATA Takashi

  Hiroshima University

• OKUMURA Koji

  Hiroshima University

• IKEUCHI Akira

  Graduate Student, Hiroshima University

• KUMAHARA Yasuhiro

  Graduate Student, Hiroshima University

• TAKADA Keita

  Graduate Student, Hiroshima University

Bibliographic Information

Other Title

• 中央構造線活断層系・重信断層の変位地形と活動履歴
• 中央構造線活断層系・重信断層の変化地形と活動履歴
• チュウオウ コウゾウセン カツダンソウケイ シゲノブ ダンソウ ノ ヘンカ チケイ ト カツドウ リレキ

Abstract

An active fault system extends for about 200 kilometers along the Median Tectonic Line (MTL) in Shikoku, Southwest Japan. Along this fault system, previous studies recognized a 10-km-long gap in the surface trace in the eastern part of the Matsuyama Plain. The gap is the largest so far found in Shi-koku. The authors newly identified very distinct strands of active faults in this gap by means of inter-pretation of high-resolution vertical aerial photographs and field work. The faults are called the Shige-nobu fault and the Shigenobu-kita fault. This paper aims: l) to depict the fault topography of the Shige-nobu and Shigenobu-kita faults; and 2) to examine the rupture history based on trench excavation across the western part of the Shigenobu fault at Takai, Matsuyama City. The results are summa-rized as follows:<br> (1) The trace of Shigenobu fault extends straight from Shitsukawa, Shigenobu Town, to Takai, Matsuyama City. The strike of the fault is N 75 to 85 degrees E. Alluvial fan surfaces are offset by this fault, and a clear fault scarplet is recognized continuously. The apparent vertical offset indicated by the height of the fault scarplet is 0.4 to 2.7 meters.<br> The Shigenobu-kita fault runs about 200 meters to the north of the Shigenobu fault. This fault, lo-cated on the margins of the plain, extends at least for 2 kilometers from Hommura to Ushibuchi, Shige-nobu Town. The M and M2 surfaces are deformed by this fault, but the L2 surface is not displaced.<br> (2) Distinct evidence of right-lateral movement is continually discernible along the Shigenobu fault. Several abandoned streams, located on the L2 surface and the L3 surface, are offset by 1.9 to 4 meters and pressure ridges occur on the northern side of the fault scarplet. The southern side of the Shigenobu fault is downthrown consistently.<br> (3) Active faults appear in a trench wall across the fault scarplet. These faults with shear plane in the trench are called F-1, F-2, and F-3. While F-2 and F-3 show no lateral offset, F-1 shows a compo-nent of lateral displacement. Therefore F-1 appears to be the main fault of the Shigenobu fault.<br> (4) The strike of F-1 is N75 to 85 degrees E, and the general dip is 85 to 90 degrees S. All horizons of the alluvial deposits in the trench are displaced by the main fault and are downthrown to the south.<br> (5) It is apparent that at least one faulting event of the Shigenobu fault occurred in the past 5, 550 years.

Journal

• Geographical Review of Japa,. Ser. A, Chirigaku Hyoron

  Geographical Review of Japa,. Ser. A, Chirigaku Hyoron 72 (4), 267-279, 1999

  The Association of Japanese Geographers

Keywords

• Median Tectonic Line
• Shigenobu fault
• active fault
• displaced landform associated with faulting
• trench excavation survey

Details

• CRID: 1390001205424216576
• NII Article ID: 10002223276
• NII Book ID: AN1016484X
• DOI: 10.4157/grj1984a.72.4_267
• ISSN: 21851735
• ISSN: 00167444
• NDL BIB ID: 4783486
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I4783486
• Web Site: https://www.jstage.jst.go.jp/article/grj1984a/72/4/72_4_267/_pdf
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
• Abstract License Flag: Disallowed