3:30 PM - 4:00 PM
[SSS15-01] Historical documents and oral transmissions on historical tsunamis in the Paciffic coast of Tohoku
★Invited Papers
Keywords:historical tsunamis, historical documents and oral transmissions, Interdisciplinary research, Keicho Oshu earthquake and tsunami
I analyzed historical tsunamis which attacked the Pacific coast of Tohoku, especially on the AD 1611 Keicho Oshu earthquake and tsunami (commonly called as the Keicho Sanriku earthquake and tsunami), based on historical documents, oral transmissions, and formation process of them.
After the AD 2011 Great East Japan Earthquake, huge historical tsunamis which damaged in the Pacific coast of Tohoku district have received attention. Some people consider the AD 869 Jogan earthquake as the precursor of AD 2011 earthquake and believe huge tsunamis occur once a thousand years. People also recognize the importance of oral transmission and the place name comes from past disasters. Previous studies pointed out the underestimation of the AD 1611 Keicho Oshu earthquake and tsunami but reinvestigated the earthquake and tsunami based on historical documents (Ebina and Imai 2014). Recently, some studies considered the AD 1454 Kyotoku earthquake as a similar event to AD 1611 Keicho oshu earthquake (Namegaya and Yata 2014; Sawai et al., 2015). Furthermore, the tsunami deposit can be correlated with this event have been found in Miyagi and Iwate Prefectures (e.g., Sawai et al., 2012; Takada et al., 2016).
According to “Sunpu Seiji Roku” and “Sunpu Ki", a vassal of the Date family said that another vassal of that encountered the tsunami on the boat during fishing and the boat was driven to the top of the mountain “Senganmatsu”. This event was estimated to occur near the mouth of Abukumagawa River in Iwanuma City. Watanabe (1998) considered this story was not true because Senganmatsu area is too high to be inundated. However, the pictorial map around Iwanuma created in Edo period indicates that Abukumagawa River was located inland from the present position of the river in that time, where a fishing village has been located since the middle ages (Ebina, 2014). Therefore, it is likely that the tsunami actually attacked the area although the story has a little exaggeration.
It is important to restore old geographical features for constraining the sizes of earthquakes and tsunamis. For instance, Fukuhara and Tanioka (2018) estimated that the magnitude of the Keicho earthquake is similar to or large than that of AD 2011 earthquake based on the data of tsunami height inferred from historical documents and oral transmissions in Miyako City, Iwate Prefecture compiled by Ebina and Imai (2014). However, the restored geographical features show that places inundated by the Keicho tsunami were located near the old channel. Therefore, the inundation in Miyako can be interpreted as the result of river run-up.
The knowledge of historical earthquakes and tsunamis along the Pacific coast of Tohoku have not been known by local residents before AD 2011 earthquake and tsunami. According to “Zishigaku Oyobi Chirigaku Kenkyu Zairyo Hokoku”, when the Imperial Science University of Tokyo (present the University of Tokyo) carried out a questionnaire about the existence of "Kaisyo" to municipal corporations all over the country in the 1890s, those in the coastal regions of Iwate answered that there are no historical records and oral transmissions on the historical earthquakes and tsunamis before AD 1856 Ansei Hachinohe-oki earthquake tsunami (Ebina and Satake 2018). This report shows that the coastal residents did not recognize that tsunamis frequently attack the Pacific coast of Tohoku in those days. Shoshin Yamana reevaluated the historical records and oral transmissions still remained in the coastal area. He carried out the survey after the AD 1896 Meiji Sanriku earthquake tsunami and wrote “Sanriku Engan Daikaisyo Torisirabe Syo”. This book includes that the description of the damage in many areas and Keicho Oshu earthquake tsunami hand-copied from the reference books of "Muto Rokuemon Syozo Komonzyo" and “Miyako Yurai Ki. These materials are obtained by the survey for influential local persons in various places. Yamana also studied the place name may be coming from driftage by past tsunamis through the interview survey to the local residents and compiled those as “Iwate Engan Kochimei Ko”. Among those 40 place names, half of them still exist (Muranaka et al., 2017). However, it is difficult to consider that many of those places were inundated by tsunamis. The possibility that some oral transmissions of those place names newly generated under the confusion by the Meiji Sanriku earthquake and tsunami.
Considering the historical viewpoint on formation processes of historical documents and oral transmissions will be useful for studies on paleo earthquakes and tsunamis.
After the AD 2011 Great East Japan Earthquake, huge historical tsunamis which damaged in the Pacific coast of Tohoku district have received attention. Some people consider the AD 869 Jogan earthquake as the precursor of AD 2011 earthquake and believe huge tsunamis occur once a thousand years. People also recognize the importance of oral transmission and the place name comes from past disasters. Previous studies pointed out the underestimation of the AD 1611 Keicho Oshu earthquake and tsunami but reinvestigated the earthquake and tsunami based on historical documents (Ebina and Imai 2014). Recently, some studies considered the AD 1454 Kyotoku earthquake as a similar event to AD 1611 Keicho oshu earthquake (Namegaya and Yata 2014; Sawai et al., 2015). Furthermore, the tsunami deposit can be correlated with this event have been found in Miyagi and Iwate Prefectures (e.g., Sawai et al., 2012; Takada et al., 2016).
According to “Sunpu Seiji Roku” and “Sunpu Ki", a vassal of the Date family said that another vassal of that encountered the tsunami on the boat during fishing and the boat was driven to the top of the mountain “Senganmatsu”. This event was estimated to occur near the mouth of Abukumagawa River in Iwanuma City. Watanabe (1998) considered this story was not true because Senganmatsu area is too high to be inundated. However, the pictorial map around Iwanuma created in Edo period indicates that Abukumagawa River was located inland from the present position of the river in that time, where a fishing village has been located since the middle ages (Ebina, 2014). Therefore, it is likely that the tsunami actually attacked the area although the story has a little exaggeration.
It is important to restore old geographical features for constraining the sizes of earthquakes and tsunamis. For instance, Fukuhara and Tanioka (2018) estimated that the magnitude of the Keicho earthquake is similar to or large than that of AD 2011 earthquake based on the data of tsunami height inferred from historical documents and oral transmissions in Miyako City, Iwate Prefecture compiled by Ebina and Imai (2014). However, the restored geographical features show that places inundated by the Keicho tsunami were located near the old channel. Therefore, the inundation in Miyako can be interpreted as the result of river run-up.
The knowledge of historical earthquakes and tsunamis along the Pacific coast of Tohoku have not been known by local residents before AD 2011 earthquake and tsunami. According to “Zishigaku Oyobi Chirigaku Kenkyu Zairyo Hokoku”, when the Imperial Science University of Tokyo (present the University of Tokyo) carried out a questionnaire about the existence of "Kaisyo" to municipal corporations all over the country in the 1890s, those in the coastal regions of Iwate answered that there are no historical records and oral transmissions on the historical earthquakes and tsunamis before AD 1856 Ansei Hachinohe-oki earthquake tsunami (Ebina and Satake 2018). This report shows that the coastal residents did not recognize that tsunamis frequently attack the Pacific coast of Tohoku in those days. Shoshin Yamana reevaluated the historical records and oral transmissions still remained in the coastal area. He carried out the survey after the AD 1896 Meiji Sanriku earthquake tsunami and wrote “Sanriku Engan Daikaisyo Torisirabe Syo”. This book includes that the description of the damage in many areas and Keicho Oshu earthquake tsunami hand-copied from the reference books of "Muto Rokuemon Syozo Komonzyo" and “Miyako Yurai Ki. These materials are obtained by the survey for influential local persons in various places. Yamana also studied the place name may be coming from driftage by past tsunamis through the interview survey to the local residents and compiled those as “Iwate Engan Kochimei Ko”. Among those 40 place names, half of them still exist (Muranaka et al., 2017). However, it is difficult to consider that many of those places were inundated by tsunamis. The possibility that some oral transmissions of those place names newly generated under the confusion by the Meiji Sanriku earthquake and tsunami.
Considering the historical viewpoint on formation processes of historical documents and oral transmissions will be useful for studies on paleo earthquakes and tsunamis.