We analyze strain rate distribution in central-northeastern Japan based on continuous GPS data before
and after the occurrence of the Great Tohoku earthquake (Mw 9.0) on March 11th, 2011, focusing on the
far-field response in the Niigata Kobe Tectonic Zone (NKTZ), an E-W contraction region along the Japan
seacoast of central Japan. Wavelength decomposition of the strain rate on the E-W direction, calculated
from GPS data, indicates that the long-wavelength pattern changed from preseismic E-W contraction
to postseismic E-W extension, representing elastic response to plate interaction at the Japan Trench.
However, the short wavelength patterns reveal a persistent localized contraction zone around northern
NKTZ before and after the Tohoku-oki earthquake. The persistent localized deformation pattern can be
reproduced by an aseismic slip on a fault cutting the lower crust and a part of the upper crust. These
results demonstrate that an inelastic process plays an essential role in the deformation of the Japan island
arc.
We analyze strain rate distribution in central-northeastern Japan based on continuous GPS data before and after the occurrence of the Great Tohoku earthquake (Mw 9.0) on March 11th, 2011, focusing on the far-field response in the Niigata Kobe Tectonic Zone (NKTZ), an E-W contraction region along the Japan seacoast of central Japan. Wavelength decomposition of the strain rate on the E-W direction, calculated from GPS data, indicates that the long-wavelength pattern changed from preseismic E-W contraction to postseismic E-W extension, representing elastic response to plate interaction at the Japan Trench. However, the short wavelength patterns reveal a persistent localized contraction zone around northern NKTZ before and after the Tohoku-oki earthquake. The persistent localized deformation pattern can be reproduced by an aseismic slip on a fault cutting the lower crust and a part of the upper crust. These results demonstrate that an inelastic process plays an essential role in the deformation of the Japan island arc.
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