A gift from Tohoku’s earthquake (March 11, 2011)

From a routine GCOE seminar, which is held in the campus regularly, there is an interesting research. Author, title, and quote of his paper are written below:

Author: Senior Fellow Shuichi Kodaira

Title: “Geophysical evidences of co-seismic fault breaking at the trench axis by the 2011 Tohoku-oki earthquake”

Quote: “From bathymetry and seismic surveys along existing profiles immediately after the earthquake and compared the data acquired before and after the 2011 earthquake. From this analysis, we detected considerable bathymetric deviation at the landward side of the trench, extending up to the trench axis and estimated that the seafloor on the landward side of the trench moved 50 m horizontally in the SE to ESE direction, and 10 m upward. This observation suggests that the plate coupled zone between earthquakes may extend at the shallowest part of the subduction zone, which is used to believe to be a stable sliding region.”

So, after last year big earthquake, has caused Japan’s trench to shifted horizontally as far as 50 m and lifted 10 m vertically. Zone meeting of the plate between each occurrence of the earthquake would extending the shallowest part of subduction zone, which is believed will make the Tohoku region shifted in a more stablestate. Or in other words in the near future Tohoku region is relatively safe from deadly major earthquakes.

Map below help us to understand the spatio-situation of Tohoku region in Japan after hit by big earthquake last year. (picture from: Shestakov, Nikolay V., Takahashi, Hiroaki, Ohzono, Mako,Prytkov, Alexander S., Bykov, Victor G., Gerasimenko, Mikhail D., Luneva, Margarita N., Gerasimov, Grigory N., Kolomiets, Andrey G., Bormotov, Vladimir A., Vasilenko, Nikolay F., Baek, Jeongho, Park, Pil-Ho, Serov, Mikhail A., Analysis of the far-field crustal displacements caused by the 2011 Great Tohoku earthquake inferred from continuous GPS observations, Tectonophysics (2011), doi: 10.1016/j.tecto.2011.12.019)

Comparison of the observed (black arrows) and computed (white arrows) horizontal coseismic displacements at the GEONET sites.

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