著者
石橋 克彦
出版者
Tokyo Geographical Society
雑誌
地学雑誌 (ISSN:0022135X)
巻号頁・発行日
vol.108, no.4, pp.399-423, 1999-08-25 (Released:2009-11-12)
参考文献数
75
被引用文献数
12 11

A large volume of historical documents in Japan show that great subduction earthquakes have repeatedly occurred along the Suruga-Nankai trough off southwest Japan since A.D. 684 with an interval of 100-200 years. They occurred as pairs of M8 events, one in the eastern half (Tokai earthquake) and another in the western half (Nankai earthquake), as was the case for the 1854 Ansei earthquakes, while sometimes occurring as single giant events like the 1707 Ho'ei earthquake. Although the space-time pattern of their recurrence is the best-known in the world, we should study more past events in order to understand the tectonophysical bases of their recurrence. In this respect I review the present understanding of historic Tokai and Nankai earthquakes and discuss related problems from the viewpoint of historical seismology. In this paper, the first of the three in all, I review the events until the early half of the 14th century. The keys to identifying older events are strong ground motion and damage in Kyoto, Nara, and Osaka, those in wider area of southwest Japan, tsunamis along the Pacific coasts of southwest Japan, typical coseismic vertical crustal movements of the Kochi plain, the Muroto and Oma'ezaki points, and the Ise and Suruga Bay coasts, temporal inactivity of specific hot springs, and aftershock activities recorded in Kyoto. The 684 Hakuho earthquake was definitely a Nankai event, and possibly included a Tokai event simultaneously (possibly Ho'ei type). The 887 Nin'na earthquake was also a definite Nankai event and was probably a Tokai event as well (Ho'ei type). The 1096 Eicho earthquake was clearly a Tokai event, but the following 1099 Kowa earthquake has some discrepancies that prevent it from being regarded as a M8 Nankai event. It is not clear yet whether great earthquakes occurred or not in the ca. 200 year intervals of 684-887 and 887-1096. It seems probable that great Tokai and Nankai earthquakes took place in the mid-13th century, but a more detailed investigation of historical seismology is required to discover the missing event.
著者
石橋 克彦 佐竹 健治
出版者
公益社団法人 日本地震学会
雑誌
地震 第2輯 (ISSN:00371114)
巻号頁・発行日
vol.50, no.appendix, pp.1-21, 1998-03-31 (Released:2010-11-17)
参考文献数
164
被引用文献数
19

We review long-term forecasts of great earthquakes along subduction zones around Japan and discuss the related problems from a paleoseismological point of view. Rich historical data in Japan show the recurrence of great earthquakes along subduction zones, particularly at the Nankai trough, for more than 1, 000 years. On the basis of such historical data and interseismic/coseismic vertical crustal movements, Imamura made a rather vague forecast of great earthquakes along the Nankai trough as early as 1933, which turned out to be successful by the occurrence of the 1944 Tonankai (Mw 8.1) and 1946 Nankai (Mw 8.1) earthquakes. After plate tectonics theory was established, the concept of seismic gap in subduction zones has been thought as a powerful tool for long-term earthquake forecasts. Great interplate earthquakes have been predicted from examinations of not only seismic gaps but also other observations such as seismic quiescence, earthquake recurrence history, current crustal deformation in coastal areas, or seismic crustal movements in geologic records. The 1973 Nemuro-oki earthquake (Mw 7.8) along the Kurile trench was predicted in 1972, although it was slightly smaller than the predicted size. The 1978 Miyagi-oki earthquake (Mw 7.6) along the Japan trench was also predicted in 1977, although the size and place were somewhat different from the prediction. The Tokai earthquake was predicted in 1976, and its occurrence has been considered imminent. Despite that short-term surveillance system has been in operation in the last 20 years, this earthquake has not occurred yet. In 1994, two great/large earthquakes occurred in subduction zones off northeast Japan, but no forecasts had been made on these. The off-Hokkaido event (Mw 8.2), whose aftershock area apparently coincides with that of the 1969 interplate earthquake (Mw 8.2), has been interpreted as an intraplate event within the subducted Pacific slab. The Sanriku-oki earthquake (Mw 7.7) was aninterplate event, but its rupture zone overlapped with a previous interplate event, the 1968 Tokachi-oki earthquake (Mw 8.2). The recurrence history of interplate earthquakes along the Nankai trough has been updated by seismo-archaeologlcal data such as liquefaction evidence at archaeoiogical sites. and it now seems more regular and can be explained by time-predictable model. In the mean time. historical data indicate that the 1605 earthquake was an unusual “tsunami earthquake” and the source process is very different from the other repeated events. This event may have been affected by a preceding large inland earthquake in 1596. Paleoseismological investigation is still very important for long-term forecast of earthquakes. Future research should emphasize to complement recurrence history of interplate earthquakes from historical as well as seismo-archaeological data, to distinguish intraplate (slab) earthquakes from interplate earthquakes in historical catalog, to investigate the co-relation between interplate and inland earthquakes, and to combine historical, geologic and other kinds of data to study earthquake recurrence as demonstrated in the Cascadia subduction zone.
著者
石橋 克彦
出版者
公益社団法人 東京地学協会
雑誌
地学雑誌 (ISSN:0022135X)
巻号頁・発行日
vol.102, no.4, pp.341-353, 1993-08-25 (Released:2010-11-18)
参考文献数
52
被引用文献数
2 3 5
著者
石橋克彦
雑誌
地震学会講演予稿集
巻号頁・発行日
vol.1, 1983
被引用文献数
2
著者
石橋 克彦
出版者
日本地球惑星科学連合
雑誌
日本地球惑星科学連合2018年大会
巻号頁・発行日
2018-03-14

●徳島県海陽町宍喰の大日寺に伝わる「円頓寺開山住持宥慶之旧記」(猪井・他,1982)の中の「当浦成来旧記書之写」(A)は,永正九年(1512)八月に洪浪が同地を襲い,浦中流失して約2200人が死亡したと記す.これは,石橋(2014,2015),Baba et al.(2017),馬場・他(2017)などが引用した『震潮記』中の記事(B)や,『大日本史料』『増訂大日本地震史料』『宍喰村誌』『海部郡誌』などが掲載する『宍喰浦旧記』(『徴古雑抄続編』所収,C)の元だと考えられる.BとCには大きな誤写があるが,Aについても幾つかの疑問がある.猪井・他(1982)が紹介した翻刻に拠って問題点を指摘する.●まず,「当浦成来旧記書之写/永正十一年正月に書記すとこれあり候」以下の中核部分に,以下のような内容的疑問がある:(1)橋より南の町は残らず流失したが死者は少なく,橋より北の町家は痛みは多くなかったが死人多く,「両町の人老若男女とも三千七百余人の相助し人一千五百余人也」という大被害のもとで,二人の城主が翌年十二月中旬までに諸寺諸社13を含む家数1805軒を再建したというが,被災地にそれほどの財的・人的・物的資源があったのか.(2)生存者1500余人に対して「町家千七百家」の再建は多すぎるだろう(しかも北町の損家は少数!).(3)北町で死者が多かったのは不自然.(4)海辺の大松原や集落周囲の山林を皆伐して建材を調達したというが,その後の高潮・豪雨災害を懸念せずに本当にやったのか.(5)「御取立(建築)の諸寺諸社」の中に祇園拝殿も記されているが,大永六年(1526)の再建棟札があるから(宍喰村誌),矛盾している.(6)城主「藤原朝臣下野守元信公 同宍喰村城主藤原朝臣孫六郎殿」と記すが,『阿波志』『宍喰町誌』によれば,愛宕山城主は藤原孫六郎元信,祇園山城主は藤原下野守持共で,名前が混乱している.●中核部分に続いて,「新寺駅路山一寺円頓寺宥慶/時に慶長十年三月四日書記す也」と末尾に記された「九ケ所寺々名附所付」などがあるが,その中の「御当代蜂須賀阿波守茂成公の御先祖蓬庵公」という記述にも次の疑問がある:(7)茂成(本名,家政)は天正十三~慶長五年(1585-1600)の藩主,以後元和六年(1620)までの藩主は子の至鎮,しかも蓬庵は家政の号だから,二重におかしい.●永正九年洪浪の記録全般に関する疑問:(8)宍喰は戦国期より前は高野山蓮華乗院の荘園だったが,文安二年(1445)の「兵庫北関入舩納帳」(林屋,1981)に木材運搬の宍喰船の記録が20件あり,その後も堺などとの交易や海部刀の輸出などが盛んだったというから(宍喰町誌),舟運被害が記されていないのは不自然ではないか.(9)宍喰の壊滅は畿内などにも影響を与えた可能性があり,他の記録があってもよいのではないか.●Aは「円頓寺開山住持宥慶之旧記」の一部だが,全体についての疑問:(10)冒頭に「元文四己未年の春駅路山円頓寺開山住持宥慶の旧記等円頓寺の二階の上鼡の巣の中より取出し候其の時々拝見の僧円頓寺住持嘉明真福寺住持大雲也旧記の本紙は円頓寺にこれあり候旧記本紙の通相違なく写取るもの也/時に元文四己未年三月十四日」とあるが,慶長十年(1605)頃の膨大な古記録(慶長九年津波のものも含む)が元文四年(1739)まで鼠の巣の中にあって,鼠害に遭わずに詳しく読めたのは不自然ではないか(後のほうの一部には「鼡喰い云々」とあるが).(11)「円頓寺開山住持宥慶」というが,同寺(大正元年<1912>大日寺に合併)の「御建立成来旧記之事」(宍喰町誌)は,「駅路山円頓寺住侶 法印快厳(花押)/慶長四己亥年正月二十八日書記之」として「当時開山住侶 <中略> 久米田寺多門院一代法印快尊弟子快厳時代也」と記すから,宥慶は開山住持ではないだろう.●以上の問題点は,書記や書写の各段階での思い違いや写し間違いの所為にされるかもしれない(翻刻ミスもありうるが,そのレベルではない).だが,不自然な記述が多く,Aの信憑性は低いのではないだろうか.ただし,Aの内容がすべて事実無根と言えるわけではなく,地元の記憶・伝承が融合されて架空の記録が作られたのかもしれず,生起年代は別として,個別的な歴史的事実は含まれているかもしれない.しかし「永正九年八月の宍喰浦洪浪災害」の実在に関しては,現段階では疑問と言わざるをえない.今後Aの記述内容を,史料学と地学的・考古学的現地調査によってさらに検討することが重要であろう.なお「宥慶之旧記」全体の精査は,慶長九年十二月十六日(1605.2.3)の宍喰の地震動・津波という歴史地震学の大問題に直結している.
著者
石橋克彦
雑誌
月刊地球
巻号頁・発行日
vol.2, pp.110-119, 1980
被引用文献数
8
著者
石橋 克彦
出版者
Tokyo Geographical Society
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.108, no.4, pp.399-423, 1999-08-25
被引用文献数
4 11

A large volume of historical documents in Japan show that great subduction earthquakes have repeatedly occurred along the Suruga-Nankai trough off southwest Japan since A.D. 684 with an interval of 100-200 years. They occurred as pairs of <I>M</I>8 events, one in the eastern half (Tokai earthquake) and another in the western half (Nankai earthquake), as was the case for the 1854 Ansei earthquakes, while sometimes occurring as single giant events like the 1707 Ho'ei earthquake. Although the space-time pattern of their recurrence is the best-known in the world, we should study more past events in order to understand the tectonophysical bases of their recurrence. In this respect I review the present understanding of historic Tokai and Nankai earthquakes and discuss related problems from the viewpoint of historical seismology. In this paper, the first of the three in all, I review the events until the early half of the 14th century. The keys to identifying older events are strong ground motion and damage in Kyoto, Nara, and Osaka, those in wider area of southwest Japan, tsunamis along the Pacific coasts of southwest Japan, typical coseismic vertical crustal movements of the Kochi plain, the Muroto and Oma'ezaki points, and the Ise and Suruga Bay coasts, temporal inactivity of specific hot springs, and aftershock activities recorded in Kyoto. The 684 Hakuho earthquake was definitely a Nankai event, and possibly included a Tokai event simultaneously (possibly Ho'ei type). The 887 Nin'na earthquake was also a definite Nankai event and was probably a Tokai event as well (Ho'ei type). The 1096 Eicho earthquake was clearly a Tokai event, but the following 1099 Kowa earthquake has some discrepancies that prevent it from being regarded as a <I>M</I>8 Nankai event. It is not clear yet whether great earthquakes occurred or not in the ca. 200 year intervals of 684-887 and 887-1096. It seems probable that great Tokai and Nankai earthquakes took place in the mid-13th century, but a more detailed investigation of historical seismology is required to discover the missing event.
著者
石橋 克彦
出版者
公益社団法人 日本地震学会
雑誌
地震 第2輯 (ISSN:00371114)
巻号頁・発行日
vol.72, pp.69-89, 2019 (Released:2020-01-31)
参考文献数
92

In leap July of the 5th year of Bunroku (in the old Japanese calendar; mostly September, 1596 in the Gregorian calendar) Bungo province (present-day Oita Prefecture) in Kyushu, southwest Japan, suffered from severe earthquake and tsunami disasters. Concerning the occurrence date of the causative earthquake, the prevailing idea is currently that a large earthquake took place on leap July 9 (September 1, 1596) in Iyo province (present-day Ehime Prefecture) in Shikoku, on the eastward opposite shore of Bungo, and another large earthquake occurred on leap July 12 in Bungo. Against this idea, I claim that a single event which can be called “the Iyo-Bungo earthquake” occurred around seven p.m. on leap July 9 in the Iyo-Bungo region based on reliable contemporary historical records. There are 69 documents on this (these) earthquake(s) printed in the existing collections of historical earthquake materials, but their values as historical records vary considerably. Since the essential principle of historiographical seismology is to utilize only reliable first-grade documents, I performed historical source criticism to select 16 contemporary materials. I referred to their original or best texts, not using texts printed in the collections. According to a record in Bungo violent ground motion collapsed shrine buildings around seven to nine p.m. on leap July 9 and a large tsunami hit Fuchu (Oita) in the twilight. In Kyoto, an autograph diary of a court noble, which is used for the first time in historical seismology, describes considerable earthquake motion around seven p.m. on leap July 9. In Hiroshima Prefecture, at Hatsuka-ichi and Itsukushima strong ground motions were felt at night on leap July 9 without damages, and at Mihara strong tremors continued from leap July 9 till 12. In Iyo, a contemporary record says a severe ground motion occurred on leap July 9 and the whole Iyo province had trouble, suggesting earthquake damages in a wide area. In Satsuma and Osumi provinces (present-day Kagoshima Prefecture), a record tells a strong earthquake on leap July 9. As a fundamental methodology of historiographical seismology, these tremors and tsunami in Bungo, Iyo, Kyoto, Hiroshima and Kagoshima on leap July 9 are considered to have been produced by an identical earthquake unless there is any counter-evidence. Leap July 12, the other proposed date of the Bungo earthquake, comes from historical materials written after 1698, which probably mistook the great Kyoto earthquake in the midnight of leap July 12 for the Bungo event. Seismic intensities are estimated to be 6 in Bungo, stronger than or equal to 5 in Iyo, 4 in Hiroshima Prefecture, 3 in Kyoto, and about 4 in Kagoshima on the JMA scale (1949-1996 version). The most simple and reasonable interpretation is that a large earthquake with the source region from around Beppu Bay off Bungo to the offshore area of western Iyo, a part of the Median Tectonic Line fault zone, took place around seven p.m. on leap July 9, whose inferred magnitude being about 7.5 (corresponding to MJMA), and the tsunami on the Bungo coast followed.