TY - JOUR
T1 - Strain anomalies induced by the 2011 tohoku earthquake (mw 9.0) as observed by a dense gps network in northeastern japan
AU - Ohzono, Mako
AU - Yabe, Yasuo
AU - Iinuma, Takeshi
AU - Ohta, Yusaku
AU - Miura, Satoshi
AU - Tachibana, Kenji
AU - Sato, Toshiya
AU - Demachi, Tomotsugu
N1 - Funding Information:
Acknowledgments. The GPS data were obtained from a research project conducted by the Japanese Nuclear Energy Safety Organization to establish evaluation techniques for seismogenic faults, the Geospatial Information Authority of Japan, and the Mizusawa VLBI Observatory of the National Astronomical Observatory of Japan. We thank Dr. J. Muto for the discussion of rheological structure in the Tohoku region. We are grateful to two anonymous reviewers and an editor, Prof. Dr. A. Hasegawa, for useful discussions and comments to improve this paper. Most of the figures were generated using the GMT software (Wessel and Smith, 1998).
PY - 2012
Y1 - 2012
N2 - 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 (Mw9.0). 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.
AB - 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 (Mw9.0). 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.
KW - 2011 tohoku earthquake
KW - Coseismic strain anomaly
KW - Strain concentration zone
KW - Structural heterogeneity
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U2 - 10.5047/eps.2012.05.015
DO - 10.5047/eps.2012.05.015
M3 - Article
AN - SCOPUS:84864605381
VL - 64
SP - 1231
EP - 1238
JO - Earth, Planets and Space
JF - Earth, Planets and Space
SN - 1343-8832
IS - 12
ER -