Econ. Environ. Geol. 2014; 47(1): 17-27

Published online February 28, 2014

© THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY

Quaternary Fault Activity of the Yangsan Fault Zone in the Samnam-myeon, Ulju-gun, Ulsan, Korea

Joo-Seok Yang and Hee-Kwon Lee*

Department of Geology, Kangwon National University, Chunchon 200-701, Korea

Correspondence to : heekwon@kangwon.ac.kr

Received: December 20, 2013; Revised: January 11, 2014; Accepted: January 23, 2014

Abstract

  We investigated space-time patterns of Quaternary fault activity of the Yangsan fault zone using ESR ages in the Samnam-myeon region, Ulsan, Korea. Some of fault gouge zones consist of well-defined bands which added to the older gouge band, indicative of reactivation. During addition of new bands, the older gouge band was inactive, which represents the type I faulting mode. ESR analyses of each band of the gouge zone allow us to construct history of fault movement. The entire fault gouge zones were reactivated by type III faulting mode giving us ESR ages of the lastest reactivation. ESR dates show temporal clustering into active and inactive periods analogous to historic and paleoseismic fault activities. ESR ages and dates of fault movements indicate migration of fault activities along the Yangsan Fault Zone. Segments of the Quaternary faults in the study area are branched in the south of Sangcheon site. The earliest record of activity in segmented faults is recorded from the western segment to the northern segment. Before 750~850 ka ago, the fault gouge zone from the western segment to the northern segment were active. At 750~850 ka ago, the fault gouge zone from the eastern segment to the northern segment were active. During 630~660 ka and 480~540 ka only the northern segment was active. After 340 ka ago, the fault gouge zone from the western segment to the northern segment were active again.

Keywords Yangsan fault zone, fault gouge, ESR dating, quaternary, pattern of fault activity

Article

Econ. Environ. Geol. 2014; 47(1): 17-27

Published online February 28, 2014

Copyright © THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY.

Quaternary Fault Activity of the Yangsan Fault Zone in the Samnam-myeon, Ulju-gun, Ulsan, Korea

Joo-Seok Yang and Hee-Kwon Lee*

Department of Geology, Kangwon National University, Chunchon 200-701, Korea

Correspondence to:heekwon@kangwon.ac.kr

Received: December 20, 2013; Revised: January 11, 2014; Accepted: January 23, 2014

Abstract

  We investigated space-time patterns of Quaternary fault activity of the Yangsan fault zone using ESR ages in the Samnam-myeon region, Ulsan, Korea. Some of fault gouge zones consist of well-defined bands which added to the older gouge band, indicative of reactivation. During addition of new bands, the older gouge band was inactive, which represents the type I faulting mode. ESR analyses of each band of the gouge zone allow us to construct history of fault movement. The entire fault gouge zones were reactivated by type III faulting mode giving us ESR ages of the lastest reactivation. ESR dates show temporal clustering into active and inactive periods analogous to historic and paleoseismic fault activities. ESR ages and dates of fault movements indicate migration of fault activities along the Yangsan Fault Zone. Segments of the Quaternary faults in the study area are branched in the south of Sangcheon site. The earliest record of activity in segmented faults is recorded from the western segment to the northern segment. Before 750~850 ka ago, the fault gouge zone from the western segment to the northern segment were active. At 750~850 ka ago, the fault gouge zone from the eastern segment to the northern segment were active. During 630~660 ka and 480~540 ka only the northern segment was active. After 340 ka ago, the fault gouge zone from the western segment to the northern segment were active again.

Keywords Yangsan fault zone, fault gouge, ESR dating, quaternary, pattern of fault activity

    KSEEG
    Apr 30, 2024 Vol.57 No.2, pp. 107~280

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