Rapid assessment of tsunami source impacts on low-lying coastal areas using offshore wave superposition and static sweep of onshore terrain

ABSTRACT Tsunami source impacts in coastal areas should be investigated thoroughly; however, investigating the associated source uncertainties can incur large computational costs. This study presents a technique for rapid assessment of the impacts and their uncertainties based on a combination of the linear wave superposition for Green’s functions and a static sweep algorithm for onshore terrain. A waveform from a tsunami source is quickly estimated at a shore based on the aforementioned superposition of single-point sources simulated by a linearized Boussinesq model. The maximum water surface elevation change in the waveform, the maximum tsunami elevation, is then determined. In addition, a digital elevation model for onshore terrain that can be inundated by a tsunami is scanned using the sweep algorithm to statically compare the tsunami and ground elevations. As a result, areas with lower ground elevation than the tsunami are quickly identified as potential tsunami hazard zones. This combined analysis is applied to assess potential tsunami sources in the Japan Sea, and the source impacts are comprehensively investigated for Sakata and Akita cities in Japan. Our analysis successfully and quantitatively indicates source impacts while considering their great uncertainty. Additionally, critical areas for expanding tsunami inundation are quickly and efficiently identified.