Submarine volcanic eruptions produce a large amount of drifting pumice around the globe at a frequency of once every several to ten years. However, there is little knowledge about what kind of eruptions produce them. Document records of large amounts of pumice washed ashore in the Nansei Islands in southwest Japan are summarized in this article, along with an assessment of their source volcanoes and eruption frequency and style. A large amount of drifting pumice has washed ashore on the Nansei Islands eight times (1778 or 1779, 1905, 1914, 1915, 1924, 1934, 1986, 2021) since the 18th century, seven of which were after the 20th century, at a frequency of several times every 100 years. This frequency is not remarkably low compared to other natural hazard events. The eruptions that provided the source of these drifting pumice were the Fukutoku-Oka-no-Ba 1904‒1905 and 1914 eruptions, the Myojin-Shou 1915 eruption, Submarine Volcano NNE of Iriomotejima 1924 eruption, the Showa Iwo-jima 1934 eruption and the Fukutoku-Oka-no-Ba 1986 and 2021 eruptions. In the 8 recorded volcanic eruptions, including the uncertain ones, 6 were due to submarine volcanic eruptions in the southern part of the Izu-Bonin Arc. It took 2 to 6 months (mostly 2 to 4 months) for drifting pumice to reach the shores of the Nansei Islands from the Izu-Bonin Arc. The eruption styles that generated a large amount of drifting pumice can be divided into three cases. (1) An eruption that ejects a large amount of pumice from the seafloor to the sea surface and causes a steam-based volcanic plume to rise at the center of the eruption. They often occur from vents with seafloor depths of several hundred meters (Submarine Volcano NNE of Iriomotejima 1924 and Showa Iwo-jima 1934), but they also occur in shallower waters (Myojin-Shou 1915). (2) An eruption that occurs in shallow water (＜50 m), with repetitive Surtseyan eruption activity that forms islands composed of large amounts of pyroclastic material, while at the same time producing large amounts of drifting pumice (Fukutoku-Oka-no-Ba 1904‒1905, 1914 and 1986). (3) An eruption that occurs in shallow water (＜50 m) and produces a volcanic plume reaching the stratosphere. This style of eruption forms an island and generates a large amount of pyroclastic material, including drifting pumice (Fukutoku-Oka-no-Ba 2021).

抄録全体を表示

地震学的には不明な点が多い琉球弧中央部について、琉球国史『球陽』の読解からその地殻変動像の復元を試みた。その結果、対象地域では18世紀後半に巨大地震が続発していたことが示唆された。1768年の地震では、地盤の強固な首里で建造物や陵墓などが損壊し、時のが王殿からの退避を余儀なくされたほか、慶良間諸島の座間味島では津波による家屋流失の後、旧阿佐村が移転を強いられるなど、大きな被害を生じた。いわゆる八重山津波として知られる1771年の震災では、沖縄島、慶良間諸島、久米島で先島より強い地震動が表現されており、那覇にも強度1程度の津波が到達していた。また西表島では余震または誘発された地震による液状化が起きている。1791年には津波地震と思われる、地震動の記述を欠いた大規模な潮位変化が沖縄島内各地で記録された。特に中城湾に面した与那原では津波の高さが10ｍを超えたとされる。これらの地震・津波は、その現象の強さと空間的広がりから、プレート境界を震源とするM8 級かそれ以上の巨大地震によって引き起こされた可能性が高い。また、それらの地異が集中した期間の前後約100年間には、匹敵する地震・近地津波の記述が無いことから、琉球海溝では巨大地震が続発する数十年の活動期と百年スケールの静穏期とが繰り返されていると考えられる。

抄録全体を表示

The four folding screens illustrated around Shuri and Naha in the Early Modern Age have two types of traditional dwelling, Nukiya and Anaya, distinctive of Okinawa prefecture. Special perspective is applied to these screens. We can easily distinguish Nukiya and Anaya on these screens according to their characteristics and illustrated areas. Nukiya may derive from the detached palace or the samurai residences. But the difference in city planning between Ryukyu Dinasty and Edo, Japan may suggest the original evolution of Nukiya.

抄録全体を表示

Table of tsunamis which occurred in and near Japan was prepared. The table consists of two parts. One part (Table 1) is the table of tsunamis caused by earthquakes, vocanic eruptions and landslides which occurred in and near Japan. Another one (Table 2) is the table of tsunamis which occurred in the Pacific Ocean and additionally invaded Japan and its vicinity.
1) Table 1.
The contents of the table are:
a) Sequential number
b) Date in the Christian and Japanese Calendar (Time in Japanese Standard Time)
c) Location of tsunami source or epicentral region together with longitude, latitude and depth of hypocenter
d) Magnitude of earthquake
e) Grade magnitude of tsunami by Dr. A. IMAMURA and Dr. K. IIDA
f) Description of earthquake and tsunami.
Magnitude of earthquake, and longitude, latitude and depth of hypocenter were taken from the “Rika-nenpyo (1968)”, the “Catalogue of major earthquakes which occurred in and near Japan, supplementary volume No. 1 (1958), No. 2 (1966) and No. 3 (1968)” and the “Zisin-geppo (1968)”.
2) Table 2.
The contents of the table are:
a), c) and f) The same content as the Table 1
b) Date in the Christian Calendar (Time in Greenwich Mean Time)
e) Grade magnitude of tsunami occurred in the Pacific Ocean and invaded Japan and its vicinity.
Magnitude of earthquake, and longitude, latitude and depth of hypocenter were taken from the “Seismicity of the Earth and Related phenomena (1954)” and the report of the U. S. Coast and Geodetic Survey.

抄録全体を表示

レジリエンスの概念には，新自由主義的な専門家本位の理論である，あるいは保守的な機能主義理論である社会-生態システム（SES）理論を母胎にしているという批判がある。元来SES理論は，生態系の均衡を前提とする機能主義への批判として出発し，複数のアトラクタを仮定する変動に関する理論である。ところが，その変動プロセスを一定の運河化された経路に固定化して考える傾向がある。そこで，本稿では，そのような経路の可塑性を主張している生物学のエピジェネティクスの理論，および記憶の曖昧さや主体的な想起に関する社会理論を参考に，SESにおけるレジリエンス概念の再構成を試みる。現在のSES理論に含まれている記憶の概念は，危機に陥った下位システムを再生する際に用いられる上位システムの結合パターンであり，すでに伝達可能なものとして構造化されている。これに対して，まだ構造化されていない曖昧な記憶を下位システムが想起し，上位システムの記憶を書き換える，そのような記憶の可塑性がありえること，そしてそれが柔軟な強さとしてのレジリエンスには，恐らく重要であることを主張する。そのような想起の事例として，八重山地域の津波とマラリアに関する（生）物の記憶について検討する。

抄録全体を表示

Okinawa prefecture, consisting of the Ryukyu Islands in the southern part of Japan archiperago, is located in the subtropics. From ancient time, Okinawa had developed trading networks with China, Korea and many Southeast Asian countries and had received cultural influence from them. As the results, it is said that the foods consumed by, and food habits of, Okinawans, have been more similar to those in such countries than in Japan. The life span of Japanese has recently become longest in the world, and it has been longer in Okinawa than in any other prefectures. In this respect, special attention has been drawn to the historical aspects of Okinawan food habits. In the literature so far, however, typical foods, recipes and food habits in specific historical periods were documented but their compiled description throughout the history was lacking. This paper aims at a comprehensive description of the various events from the ancient time to the present to demonstrate their interrelation in a chronicle. Major a pects treated are introduction of foods, food production systems, food-processing, trades, marketing activities, food consumptions, religious roles of food services, and famines caused by natural and man-made disasters in relation to food habits.

抄録全体を表示