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Structural analysis of coseismic normal fault zones of the 2011 M (sub w) 6.6 Fukushima earthquake, northeast Japan

Aiming Lin, Shinji Toda, Gang Rao, Satoru Tsuchihashi and Bing Yan
Structural analysis of coseismic normal fault zones of the 2011 M (sub w) 6.6 Fukushima earthquake, northeast Japan (in 2011 Tohoku earthquake and tsunami, Thorne Lay (editor), Yushiro Fujii (editor), E. Geist (editor), K. Koketsu (editor), J. Rubinstein (editor), T. Sagiya (editor) and M. Simons (editor))
Bulletin of the Seismological Society of America (May 2013) 103 (2B): 1603-1613


The 2011 M (sub w) 6.6 Fukushima earthquake occurred in Iwaki City, approximately 250 km southwest of the epicenter of the 2011 M (sub w) 9.0 Tohoku (Japan) earthquake, and produced two subparallel approximately 15-23-km-long surface rupture zones with distinct displacements along two pre-existing normal faults: the Shionohira and Yunodake faults, which strike north-northwest-south-southeast and northwest-southeast (both dipping southwest), respectively. Field investigations and structural analysis of the coseismic shear zones developed within the Shionohira and Yunodake fault zones, reveal that (1) the coseismic shear zones consist of a fault core that includes a narrow fault gouge zone of <10 cm in width (generally 1-5 cm), a fault breccia zone of <50 cm in width, and a damage zone of 5-50 m in width that is composed of cataclastic rocks, fractures, and subsidiary faults; (2) the foliations characterized by S-C fabrics developed in the shear zones indicate a dominantly normal fault-slip sense, consistent with that observed along the coseismic surface ruptures; and (3) veinlet cataclastic rocks composed of unconsolidated fault gouges and fine-grained materials occur as simple discrete veinlets and multiple, cross-cutting, interconnected networks of veinlets. These newly documented structural characteristics for two coseismic fault/shear zones and associated cataclastic rocks indicate that the locations of coseismic slip zones associated with the 2011 Fukushima earthquake were controlled by pre-existing fault/shear zones central to the Shionohira and Yunodake faults, which have repeatedly moved as seismogenic normal faults since the timing of formation of associated cataclastic rocks. Our results demonstrate that the structural analyses of coseismic shear/fault zones provide a powerful tool to study the nature and active faulting history of seismological faults.

ISSN: 0037-1106
EISSN: 1943-3573
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 103
Serial Issue: 2B
Title: Structural analysis of coseismic normal fault zones of the 2011 M (sub w) 6.6 Fukushima earthquake, northeast Japan
Title: 2011 Tohoku earthquake and tsunami
Author(s): Lin, AimingToda, ShinjiRao, GangTsuchihashi, SatoruYan, Bing
Author(s): Lay, Thorneeditor
Author(s): Fujii, Yushiroeditor
Author(s): Geist, E.editor
Author(s): Koketsu, K.editor
Author(s): Rubinstein, J.editor
Author(s): Sagiya, T.editor
Author(s): Simons, M.editor
Affiliation: Shizuoka University, Graduate School of Science and Technology, Shizuoka, Japan
Affiliation: University of California at Santa Cruz, Department of Earth and Planetary Sciences, Santa Cruz, CA, United States
Pages: 1603-1613
Published: 201305
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 36
Accession Number: 2013-044438
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch maps
N36°55'00" - N37°04'60", E140°40'00" - E140°49'60"
Secondary Affiliation: International Institute of Seismology, JPN, JapanU. S. Geological Survey, USA, United StatesEarthquake Research Institute, JPN, JapanDisaster Mitigation Research Center, JPN, JapanCalifornia Institute of Technology, USA, United StatesKyoto University, JPN, Japan
Source Note: Supplement
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201328
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