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Research paper : Reconstruction of the 869 Jogan tsunami and lessons from the 2011 Tohoku earthquake (Y. Okamura)−245−Synthesiology - English edition Vol.5 No.4 (2013) (Fig. 6). As a result, we presumed that a tsunami inundates all the way to the distribution zone of the tsunami deposits by an earthquake of magnitude 8.4 caused by a 7 m slip (fault displacement) of an area with length of 200 km and width of 100 km along the plate boundary at a depth of 15-46 km off the Miyagi to Fukushima Prefectures.[17][18] However, this earthquake source fault model did not consider the possibility that the tsunami inundation zone was wider than the distribution zone of tsunami deposits. Also since the northern and southern limits of the inundation zone were unclear, there was a possibility that the scale of the earthquake might be greater[12] (Fig. 7).5 Jogan Earthquake model evaluated by the actual earthquakeOne of the major reasons that the earthquake prediction research does not advance is because actual experiments cannot be conducted. The currently used science and technology were built upon repeated experiments, and there must have been numerous failures. On the other hand, the scale of a natural phenomenon is incomparably large. While rock deformation experiments can be done in the laboratory, a natural earthquake cannot be predicted by such experimental results only. The dynamic characteristics of deep underground rock is becoming clarified by the rock deformation experiments under high temperature and pressure conditions, but there are many unknowns about the actual deep underground conditions such as the diversity of rock types and the presence of fluid. It is impossible to recreate such natural conditions perfectly in the laboratory. Therefore, seismology has been advanced by the analysis of earthquakes that actually occurred. Even if the images of past earthquakes are recreated based on the tsunami deposits, they cannot be verified unless an earthquake actually occurs. The 2011 Tohoku-oki Earthquake was the first earthquake and giant tsunami that occurred in the area where the past earthquakes have been estimated by researches using the tsunami deposits, and it has provided an opportunity to examine the reliability of our paleoseismological research.The Jogan Earthquake model estimated to be of magnitude 8.4 or greater was smaller than the magnitude of the 2011 Tohoku-oki Earthquake. However, in the Sendai Plain, there was no major difference between the inundation areas of tsunamis by the 869 and 2011 earthquakes [19] (Fig. 8). According to the study of tsunami deposits formed by the 2011 earthquake, it was shown that the tsunami (seawater) reached about 1~2 km inland further than the area where tsunami deposit (sand layer) was formed.[19] This finding is extremely important for the estimation of the magnitude of the tsunami from the distribution of tsunami deposits. It is necessary to reevaluate the magnitude of the Jogan tsunami taking this difference into account. It is expected that the Fig. 5 Example of calculation of the Jogan tsunami source model (edited from References [17] and [18])The tsunami was calculated by assuming the fault planes with different scale on the subducting Pacific Plate offshore of Tohoku.Ishinomaki PlainSendai PlainPlate boundary typeNormal fault typeTsunami earthquake typeMinoura et al.HatoriWatanabeHatoriWatanabe20051978200519781531460 km0 kmDepthDepthJapan TrenchJapan TrenchOdakaUkedo7 m7 mMw 8.4Mw 8.4Model 10Model 10Inter plate d15_L200_W100_u7Inter plate d15_L200_W100_u7Ishinomaki PlainSendai PlainPlate boundary typeNormal fault typeTsunami earthquake typeMinoura et al.HatoriWatanabeHatoriWatanabe20051978200519781531460 km0 kmDepthDepthJapan TrenchJapan TrenchOdakaUkedo7 m7 mMw 8.4Mw 8.4Model 11Model 11Inter plate d31_L200_W100_u7Inter plate d31_L200_W100_u7Ishinomaki PlainSendai PlainPlate boundary typeNormal fault typeTsunami earthquake typeMinoura et al.HatoriWatanabeHatoriWatanabe20051978200519781531460 km0 kmDepthDepthJapan TrenchJapan TrenchOdakaUkedo5 m5 mMw 8.3Mw 8.3Model 5Model 5Inter plate d15_L200_W100_u5Inter plate d15_L200_W100_u5Ishinomaki PlainSendai PlainPlate boundary typeNormal fault typeTsunami earthquake typeMinoura et al.HatoriWatanabeHatoriWatanabe20051978200519781531460 km0 kmDepthDepthJapan TrenchJapan TrenchOdakaUkedo5 m5 mMw 8.3Mw 8.3Model 6Model 6Inter plate d31_L200_W100_u5Inter plate d31_L200_W100_u5Ishinomaki PlainSendai PlainPlate boundary typeNormal fault typeTsunami earthquake typeMinoura et al.HatoriWatanabeHatoriWatanabe20051978200519781531460 km0 kmDepthDepthJapan TrenchJapan TrenchOdakaUkedo5 m5 mMw 8.1Mw 8.1Model 1Model 1Normal fault typeNormal fault typeIshinomaki PlainSendai PlainPlate boundary typeNormal fault typeTsunami earthquake typeMinoura et al.HatoriWatanabeHatoriWatanabe20051978200519781531460 km0 kmDepthDepthJapan TrenchJapan TrenchOdakaUkedo5 m5 mMw 8.1Mw 8.1Model 2Model 2Tsunami earthquake typeTsunami earthquake typeIshinomaki PlainSendai PlainPlate boundary typeNormal fault typeTsunami earthquake typeMinoura et al.HatoriWatanabeHatoriWatanabe20051978200519781531460 km0 kmDepthDepthJapan TrenchJapan TrenchOdakaUkedo5 m5 mMw 8.1Mw 8.1Model 3Model 3Inter plate d15_L200_W50_u5Inter plate d15_L200_W50_u5Ishinomaki PlainSendai PlainPlate boundary typeNormal fault typeTsunami earthquake typeMinoura et al.HatoriWatanabeHatoriWatanabe20051978200519781531460 km0 kmDepthDepthJapan TrenchJapan TrenchOdakaUkedo5 m5 mMw 8.1Mw 8.1Model 4Model 4Inter plate d31_L200_W50_u5Inter plate d31_L200_W50_u5

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