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

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• 作者：Mako Ohzono ; Yasuo Yabe ; Takeshi Iinuma ; Yusaku Ohta…
• 关键词：Coseismic strain anomaly ; 2011 Tohoku Earthquake ; structural heterogeneity ; strain concentration zone
• 刊名：Earth, Planets and Space
• 出版年：2012
• 出版时间：December 2012
• 年：2012
• 卷：64
• 期：12
• 页码：1231-1238
• 全文大小：3468KB
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• 作者单位：Mako Ohzono (1)
  Yasuo Yabe (2)
  Takeshi Iinuma (2) (3)
  Yusaku Ohta (2)
  Satoshi Miura (4)
  Kenji Tachibana (2)
  Toshiya Sato (2)
  Tomotsugu Demachi (2)
  
  1. Institute of Seismology and Volcanology, Graduate School of Science, Hokkaido University, Sapporo, 060-0810, Japan
  2. Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
  3. International Research Institute of Disaster Science, Tohoku University, Sendai, 980-8578, Japan
  4. Earthquake Research Institute, the University of Tokyo, Tokyo, 113-0032, Japan
  
• 刊物类别：Earth Sciences, general; Geology; Geophysics/Geodesy;
• 刊物主题：Earth Sciences, general; Geology; Geophysics/Geodesy;
• 出版者：Springer Berlin Heidelberg
• ISSN：1880-5981

文摘

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 (M _w 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. Key words Coseismic strain anomaly 2011 Tohoku Earthquake structural heterogeneity strain concentration zone