THE GENERATION OF WAVES CAUSED BY LONG-PERIOD GROUND MOTION AT A REMOTE LOCATION FROM EPICENTER

Abstract

 This work aims to ascertain the wave behavior and possible damage in a lake or a bay caused by the effect of long-period ground motion using the same numerical analysis. The generation of waves which are affected by long-period ground motion is a new concept. In general, when an earthquake occurs in a marine area, tsunami disaster is of special concern as water can damage coastal regions. However, in fact, not only tsunami but also high waves caused by long-period ground motions were generated at Sai Lake in Yamanashi Prefecture about 470km far from the epicenter of the Tohoku earthquake (Mw9.0) and this phenomenon has not received sufficient attention up to now. According to the field survey, there is evidence that waves of up to 1.0m height were generated. These 1.0m height waves were accurately simulated by the numerical model, whose governing equations are the non-linear shallow water equations. Furthermore, this model was applied to Tokyo Bay against the possible future Tokai and Tonankai earthquakes which are forecasted to take place within the next 20 years. As a result, the wave height generated by the long-period ground motion is less than 1m. These waves, although they will not lead to inundation of coastal areas, are irregularly generated and can shake small boats or float bridges, and it is important for people in the area to pay attention to this following the earthquake.