Abstract
Water level fluctuations resembling long period tsunami waves, which differ from normal wind waves, were observed immediately after the Great East Japan Earthquake of 2011 in multiple locations, such as lakes in Yamanashi Prefecture, the fjords of Norway, and other sites located far away from the epicenter. Very little research on similar abnormal water level fluctuations has been conducted thus far and, in many cases, these studies have treated the phenomena as seiches. However, researchers have not established concrete wave development mechanisms and evaluation methods, and their awareness of this phenomenon and disaster prevention remains low. In this study, we sought to select a quantitative impact assessment method and learn more about this phenomenon. We used previous research and eyewitness accounts to judge that onsite slosh dynamics caused the waves to develop, and we attempted to recreate this phenomenon using a 3-D slosh dynamic analysis. After comparing laboratory results to verify the validity of the analysis, we recreated past examples of waves and also made future predictions. As a result, we were able to recreate abnormal water level fluctuations based on this method. In addition, we identified water damage risks to inland lakes and waterways of inner parts of bays. These are different from risks posed by tsunamis. It is forms immediately after the onset of an earthquake.
