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Strain anomalies induced by the 2011 Tohoku Earthquake (Mw 9.0) as observed by a dense GPS network in northeastern Japan

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Title: Strain anomalies induced by the 2011 Tohoku Earthquake (Mw 9.0) as observed by a dense GPS network in northeastern Japan
Authors: Ohzono, Mako Browse this author
Yabe, Yasuo Browse this author
Iinuma, Takeshi Browse this author
Ohta, Yusaku Browse this author
Miura, Satoshi Browse this author
Tachibana, Kenji Browse this author
Sato, Toshiya Browse this author
Demachi, Tomotsugu Browse this author
Keywords: Coseismic strain anomaly
2011 Tohoku Earthquake
structural heterogeneity
strain concentration zone
Issue Date: 2012
Publisher: Terra Scientific Publishing Company
Journal Title: Earth, Planets and Space
Volume: 64
Issue: 12
Start Page: 1231
End Page: 1238
Publisher DOI: 10.5047/eps.2012.05.015
Abstract: We have evaluated an anomalous crustal strain in the Tohoku region, northeastern Japan associated with a step-like stress change induced by the 2011 off the Pacific coast of Tohoku Earthquake (Mw 9.0). Because the source area of the event was extremely large, the gradient of the observed eastward coseismic displacements that accompanied uniform stress change had a relatively uniform EW extension in northeastern Japan. Accordingly, the deformation anomaly, which is determined by subtracting the predicted displacement in a half-space elastic media from the observed displacement, should reflect the inhomogeneity of the rheology, or stiffness, of the crust. The difference of the EW extension anomaly between the forearc and backarc regions possibly indicates a dissimilarity of stiffness, depending on the crustal structure of the Tohoku region. The Ou-backbone range - a strain concentration zone in the interseismic period - shows an extension deficit compared with predictions. A low viscosity in the lower crust probably induced a relatively small extension. Meanwhile, the northern part of the Niigata-Kobe tectonic zone, another strain concentration zone, indicates an excess of extensional field. This is probably caused by a low elastic moduli of the thick sedimentation layer. The detection of strain anomalies in the coseismic period enables a new interpretation of the deformation process at strain concentration zones.
Type: article
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 大園 真子

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