The purpose of this study is to verify the fault length and earthquake magnitude of the Iyo-Bungo earthquake in 1596 estimated by Ishibashi (2019) using historical documents written in the same period. According to Ishibashi (2019), the length of the source fault was estimated to have been less than 100 km and the earthquake magnitude was roughly estimated to have been around 7.5. In order to attempt to reproduce the interpretation, we conducted two different strong ground motion simulations: the attenuation equation method and the characterized source model method, both used in the Headquarters for Earthquake Research Promotion. We simulated earthquake ground motions based on several source fault models including estimation by Ishibashi (2019). For the length of the fault, a 100 km length corresponding to the Iyonada segment of the Median Tectonic Line active fault system was the first model and 130 km and 160 km models extending onshore to the northeast were taken into account as epistemic uncertainties. Regarding the dip angle of the fault, both 40 and 90 degree models were considered also as epistemic uncertainties. Our calculation with other uncertainties shows that the models with a fault length of 100 km with a dip angle of 90 or 40 degrees are consistent with the seismic intensity and seismogenic fault length of offshore fault estimated by Ishibashi (2019) based on reliable first-grade documents. If low-certainty intensity estimates by Ishibashi (2019) are used to evaluate fault length in our calculation, the possibility of 130 or 160 km length models with additional onshore faults will remain. Our results show that the strong ground motion simulation could reinforce the expert’s interpretation of historical documents and propose quantitative source fault models for historical earthquakes.