2002 Volume 54 Issue 4 Pages 431-440
Three earthquakes and accompanying tsunamis of 1704, 1793 and 1804 hit the coastal area of the Aomori-Akita districts in the northern part of Japan Sea, causing several hundreds of fatalities and serious damages to houses and ships. In this study, we simulate the generation and the propagation of these tsunamis by assuming several fault models, and determine a set of fault parameters for each earthquake that best fits the observed distributions of tsunami heights and crustal uplifts. The fault model previously proposed by Sato (1980) for the 1704 Iwadate earthquake generally explains the observed tsunami heights, but a similar model with the fault length 3km longer towards the north is more consistent with the reported crustal uplift at Henashi peninsula. For the 1793 Ajigasawa earthquake, a fault model lying off the coast of Tsugaru peninsula better explains the observed tsunami heights around Ajigasawa. The tsunami simulation also corroborates the observation that tsunami caused by the event might flush into the Jyusan Lake. Among several fault models tested for the 1804 Kisakata earthquake, a fault model located most offshore shows the best agreement with the observed distribution of tsunami heights. The tsunami simulations for the 1704 Iwadate and 1804 Kisakata earthquakes show that the tsunamis are largely amplified at Oga peninsula. The amplification is ascribed to an energy concentration by the reflection in the 1704 Iwadate tsunami and the edge wave trapped in the shallow sea in the 1804 Kisakata tsunami, respectively. Both are important mechanisms affecting the heights of tsunamis along the Japan Sea coast.
