Abstract
A huge number of people living in areas below sea level in Tokyo, Nagoya and Osaka etc. are shielded from inflow sea water by river and sea dikes. The dikes face the Nankai Trough earthquake which occurs in high probability in a few dozens years future, therefore it is necessary to estimate the seismic resistance of the embankments during a long time duration earthquake with satisficate accuracy. As the detail seismic assessments of the exceedingly-long dikes are impossible in practice, we need a facile method to estimate the seismic resistance of the embankment for the first screening. In this study, we evaluated the ground motions during the past three earthquakes, the 2011 off the Pacific coast of Tohoku earthquake, the 2003 Northern Miyagi Earthquake and the 1978 off Miyagi Earthquake, and conducted one dimensional earthquake response analyses with equivalent linear model. We calculated the liquefaction indexes for the dikes of the Naruse river in Miyagi prefecture during the three earthquakes based on the cumulative damage concept. The index values are good agreement with the damage of the embankments of each three earthquake. The results show that the simplified methodology has a possibility for the first screening of seismic resistant of an embankment with liquefaction.
