Abstract
The purpose of this study was to verify the fault modeling in the source region of the 1940 Shakotan-Oki earthquake, which was caused by the active marine faults offshore Japan. The tsunami wave heights simulated from fault models proposed by previous studies were lower than the observations, which made it difficult to explain the historical tsunami records of the 1940 Shakotan-Oki earthquake. However, the application of appropriate slip magnitudes in the fault models may be able to explain these differences. In this study, we constructed a new fault model using marine seismic industry data and geological and geophysical data compiled by the Off shore Fault Evaluation Group, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), as part of the Project for off shore fault evaluation, the Ministry of Education, Culture, Sports, Science and Technology (MEXT). The marine seismic industry data included information from a new fault that was located to the north of the existing fault investigated in the previous studies. We adjusted the geometrical continuity of these faults, whereby the magnitude of the fault slip was increased. We applied the standard scaling laws based on strong ground motion for the fault parameters. The validity of the fault model was examined from a comparison of tsunami wave heights in the Japanese coastline between historical observation records and the tsunami simulation analysis, and quantified with scale and variance parameters referred to as Aida's K and κ. Based on the results, the simulated tsunami wave heights using the new model approached the heights observed in the historical records, thus indicating the validity of the model for accurately modeling the source region. In future studies, more reasonable results are expected by considering asperities and the fault parameters located in the shallow part of the source region.
