著者

茂木 昭夫

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.79, no.5, pp.243-265, 1970-10-25 (Released:2009-11-12)

参考文献数

47

被引用文献数

6 6

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The Philippine Sea is bounded on the west by the southern half of Japan, the Ryukyu Islands and the Philippines, and on the east by the arcuate seafloor ridge extending from Japan to the Palau Islands through the Mariana Islands. Both arcuate structures are associated with deep sea trench, island arcs, volcanic activity, deep focus earthquakes and negative gravity anomalies. This abyssal deep basin which consists of the oceanic crust is separated into the east and the west basin by the Kyushu-Palau Ridge. The east basin is somewhat shoaler, and can be divided by the central narrow zone at 23°N into two parts, Shikoku Basin and West Mariana Basin, which gradually rise toward the Honshu-Mariana Ridge. There are, however, several seamounts, called the Kinan Seamount Chain, arranged in NNW-SSE direction in the Shikoku Basin. And on its southern extension, there are several troughs, called the West Mariana Trough, arranged is N-S direction. The Shikoku Basin is composed of the smooth floor of the northeastern part and the mountainous area of the southwestern part. The West Mariana Basin is also divided into the abyssal plain on the east and abyssal hill region on the west. And the West Mariana Trough is running on its boundary.The west basin, Philippine Basin, is unusually deep. A region of rugged topography which can be termed the Daito Ridges lies at the northernmost part of the basin. These several parallel ridges elongate from the respective coral islands to southeastward intervening narrow depressions. There are flat plains at the depth of about 1500, 2000 and 3000 m on the northern side of each of the ridges. There is the striking feature, called Central Basin Fault, in the central part of the Philippine Basin. Central Basin Fault which is the low ridge associated with trough in the NW-SE direction separate the Philippine Basin into the north basin and the south basin. On the Philippine Basin floor, the most extensive area is abyssal hill region. Abyssal plains are developed only in limited localities such as the west side of the northern arc of the Kyushu-Palau Ridge.From the description on the submarine topography of the Philippine Sea the author concluded as follows.(1) A few ridges and seamounts not associated with trench are running parallel to the Ryukyu-Philippine Arc and Izu-Mariana Arc : one Kyushu-Palau Ridge, two Kinan Seamount Chain-West Mariana Trough, three Nishi-Shichito Ridge-West Mariana Ridge. These ridges close the space eastward. And basements of basins which intervened between each ridges rise toward the east.(2) There are another ridges having unusual trend. The Daito Ridges have E-W trend and the minor ridges on the Izu Ridge have the NE-SW trend.The numerous minor ridges which construct the abyssal hill region also have the E-W trend on the northern part of the Philippine Sea, although its trend changes to the N-S trend southward gradually. These trends are correspond to the Southwest Japan Arc.(3) Ridges with E-W trend are cut by the ridges with N-S trend, alike the Japan Arc crossed by the Izu-Mariana arc.(4) Kyushu-Palau Ridge consists of two arcs, northern arc parallel to the Ryukyu Arc and southern arc parallel to the Philippine Arc. These two arcs are separated by the Central Basin Fault. Another possible fault runs from the depression in the east side of the northern Kyushu-Palau Ridge to the junction of the Izu-Ogasawara Arc and the Mariana Arc. The southern arc (Mariana) remarkably projects to the southeast along this fault.(5) Abyssal hill provinces in the Philippine Sea occupy the western half of each basins usually. Some of the flat plains occupying the eastern half appear to the archipelagic apron which is constructed by the eruption on the concave side flank of the arcuate ridges.

著者

茂木 昭夫 土出 昌一

出版者

特定非営利活動法人 日本火山学会

雑誌

火山.第2集 (ISSN:24330590)

巻号頁・発行日

vol.23, no.1, pp.91-100, 1978-04-15 (Released:2018-01-15)

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The Hydrographic Department of Maritime Safety Agency has been conducting surveillance and investigation about the activity of submarine volcanoes in the adjacent seas of Japan. There are three active submarine volcanoes belonging to Middle Mariana ridge; Fukutoku oka-no-ba about 4 miles mrtheastward, Minami-Hiyosi Kaizan about 50 miles south-south eastward and Fukuzin Kaizan about 180 miles southeastward from Minami-Io Sima Is. respectively. Discolored water around them is found at irregular intervals, which should be caused by submarine volcanic eruption. The Hydrographic Department conducts to research their activity using remote sensing techniques such as aerial photogrammetry, multiband photographs and thermal camera by an airplane. A survey ship also is used to research bathymetry, geological structure, geomagnetism and gravity in the submarine volcanic areas at the rest time of the volcanic activity. In this paper, wedescribe about the system of surveillance and investigation to them together with the record of recent submarine volcanic eruptions in the adjacent seas of Japan.

著者

茂木 昭夫

出版者

THE TOHOKU GEOGRAPHICAL ASSOCIATION

雑誌

東北地理 (ISSN:03872777)

巻号頁・発行日

vol.9, no.2, pp.43-46, 1956