The Japan Academy

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Vol. 91 No. 6 (2015)

Vol. 91 No. 6 (2015)

Propagation of the 2011 Tohoku Tsunami

  The huge tsunami generated by the 2011 Tohoku Earthquake developed tremendous damage to coastal areas in East Japan. Characteristics of the earthquake and the tsunami have been studied on the basis of scientific data of seismometers, tide gages and ground displacements estimated by Global Navigation Satellite System network. However, reliable data of tsunami on land are relatively few compared with shaking/ground motion data. Post-tsunami surveys are therefore important to complement tide gage data. Since the affected area was large, the post tsunami surveys should be performed quickly under a good coordination of multiple teams to cover the whole affected area. Collaboration among scientists, engineers and government officials was well organized by a smart data sharing scheme on the Internet. Based on laborious but smartly organized surveys, tsunami height database was disseminated on the web immediately after the survey. These data are utilized for tsunami analysis as well as rescue and recovery activities.
  The cover picture illustrates snapshots of the 2011 Tohoku Tsunami computed by a numerical model. The panel (a) illustrates the bathymetry with epicenters of historical earthquakes. The tsunami source of the 2011 tsunami (panel b) was assumed by a model estimated on the basis of tide gage and watermark height database. Many interesting features of the tsunami are visualized in the computation, such as emission of tsunami energy in east-west directions (panel c), concentration of tsunami energy by local bathymetry (panel d), reflection of tsunami from the shore and nearshore entrapment of tsunami even several hours after the earthquake as represented by arrows in panels (e) and (f). Such tsunami simulation is used in many cities and towns as fundamental data for tsunami hazard mitigation. A review article by Prof. Shinji Sato in this issue (pp. 262-272) discusses characteristics of the massive tsunami and future directions of tsunami disaster mitigation.

Nobuo Shuto
Professor Emeritus, Tohoku University