Amir Salaree, Yihe Huang

The 2011 Tohoku earthquake created a moderate tsunami in the back-arc Sea of Japan basin. This tsunami went largely unnoticed due to its small size and the significant coverage of the large fore-arc waves. We present a physical dislocation model for the excitation of back-arc tsunamis and identify fault dip as the main geometrical contributor to the propagation of back-arc tsunamis. Using numerical simulations and data from the 2011 event, we show that a combination of near- to intermediate-field horizontal and vertical dislocations as well as transient surface waves is necessary to reconstruct the back-arc propagation. We then simulate potential future earthquakes in the Japan trench and Nankai trough to investigate the back-arc tsunami hazard in the Sea of Japan. Our results show that the coseismic excitation of back-arc tsunamis can result in considerable waves exceeding 1 m from megathrust earthquakes.