Abstract
The occurrence of the 2011 Tohoku earthquake (Mw9.0) along the Japan Trench motivated us to hypothesize an equally gigantic earthquake along the Nankai Trough, which is another plate boundary close to the coast of Japan. The evaluation of strong ground motions for such an earthquake should be based on a source model whose applicability for gigantic earthquakes has been demonstrated using existing strong motion records including those from the Tohoku earthquake. In this article, strong ground motions for a scenario earthquake with Mw9.0 along the Nankai Trough are evaluated using a source model called the "SPGA model", which can reproduce strong ground motions from gigantic earthquakes quite accurately. Because it is difficult to predict the locations of SPGAs, many cases are considered with different distributions of the SPGAs. The result indicates that the ground motions are strongly dependent on the locations of the SPGAs. When an intense SPGA is close to the target site, the ground motions can be much more intense than those conventionally assumed for the design of infrastructures.
