TY - JOUR
T1 - Geodetic evidence of viscoelastic relaxation after the 2008 Iwate-Miyagi Nairiku earthquake
AU - Ohzono, Mako
AU - Ohta, Yusaku
AU - Iinuma, Takeshi
AU - Miura, Satoshi
AU - Muto, Jun
N1 - Funding Information:
Acknowledgments. GPS data were provided by a research project conducted by the Japanese Nuclear Energy Safety Organization (JNES) in order to establish the evaluation techniques of seismogenic faults, the Geospatial Information Authority of Japan, and the Mizusawa VLBI Observatory of the National Astronomical Observatory of Japan. We would like to thank K. Tachibana, T. Sato, and Dr. T. Demachi for their efforts in maintaining the GPS sites at Tohoku University. In addition, we would like to thank Dr. A. Freed and Dr. T. Sato for the useful discussion. We are also grateful to Dr. H. Suito and an anonymous reviewer, and editor Dr. T. Sagiya for useful discussions and comments to improve this paper. The present study was partly supported by a Grant-in-Aid for JSPS Fellows (No. 2056071) and Grant-in-Aid for Young Scientists (B: No. 22740287).
PY - 2012
Y1 - 2012
N2 - Continuous GPS observations, for over two years, detected long-term postseismic deformation after the 2008 Iwate-Miyagi Nairiku earthquake (M j 7.2). The displacement field exhibits ESE-WNW shortening and subsidence near the focal area. These features are attributed to a viscoelastic relaxation caused by the mainshock. A simple two-layered structural model, which consists of an elastic layer having a thickness of 19.0-23.5 km and an underlying Maxwell viscoelastic layer having a viscosity of 2.4-4.8 × 1018 Pa s, explains the far-field deformation pattern, which probably reflects the viscoelastic response exclusively. These estimated parameters are consistent with the deeper limit of the seismogenic layer in the upper crust and the previous rheological model in northeastern Japan. However, near-field deformation requires additional sources in order to reproduce the observed postseismic deformation, such as long-term afterslip and/or a complicated response due to the highly heterogeneous structure suggested by seismic tomography studies.
AB - Continuous GPS observations, for over two years, detected long-term postseismic deformation after the 2008 Iwate-Miyagi Nairiku earthquake (M j 7.2). The displacement field exhibits ESE-WNW shortening and subsidence near the focal area. These features are attributed to a viscoelastic relaxation caused by the mainshock. A simple two-layered structural model, which consists of an elastic layer having a thickness of 19.0-23.5 km and an underlying Maxwell viscoelastic layer having a viscosity of 2.4-4.8 × 1018 Pa s, explains the far-field deformation pattern, which probably reflects the viscoelastic response exclusively. These estimated parameters are consistent with the deeper limit of the seismogenic layer in the upper crust and the previous rheological model in northeastern Japan. However, near-field deformation requires additional sources in order to reproduce the observed postseismic deformation, such as long-term afterslip and/or a complicated response due to the highly heterogeneous structure suggested by seismic tomography studies.
KW - Geodetic observation
KW - Inland earthquake
KW - Postseismic deformation
KW - Viscoelastic response
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U2 - 10.5047/eps.2012.04.001
DO - 10.5047/eps.2012.04.001
M3 - Article
AN - SCOPUS:84876241617
VL - 64
SP - 759
EP - 764
JO - Earth, Planets and Space
JF - Earth, Planets and Space
SN - 1343-8832
IS - 9
ER -