Submarine geology off Okinawa Island.
The Hydrographic Department, M.S.A., carried out detailed survey for submarine geology and topography in the vicinity of the Okinawa sea area in 1975 and 1976. The surveyed area, located in the central area of Nansei-syoto (Ryukyu island are) is shown in figure 1, and survey lines are shown in figure 3. The survey lines are 2 nautical mile spacing in an E-W direction, and echo-sounding and seismic profiling by the air-gun method, etc., have been done on all lines. The submarine topographic chart and submarine geological map are shown in figures 4 and 5, which were compiled by the results of this survey. In general, the submarine topography and geological structure in this area is controlled by the NE-SW direction of the main structure of the island arc. This area is divided into four geological provinces. The trench wall region of the outer landward zone, has well developed submarine canyons. The Island region, being the axis zone of the island arc, has several small basins which formed by tilting movements. The southwestern end of the survey area lined by the Kerama Gap across the island arc in a WNW-ESE direction. The southern end of the Gap terminated by the escarpment of the Kerama fault. There are many small sea knolls that seem to be Quaternary volcanoes in the NE-SW direction inside of the Island region. The Okinawa Trough partly appears in the northwestern margin of area. The tectonic movement in the NE-SW direction is considered to have become active in the late Miocene to Pliocene,and the tectonics of the Kerama fault movement crossing the former direction became active from after the Pliocene to the early Pleistocene.
| Main Authors: | , , |
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| Format: | Journal Contribution biblioteca |
| Language: | Japanese |
| Published: |
1982
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| Online Access: | http://hdl.handle.net/1834/16229 |
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