水路部研究報告第26 号平成 2 年 3 月30 日 REPORTOFHYDROGRAPHICRESEARCHESNo.26March,1990. ヤッブ海溝北端部の海底地形T 岩淵洋*・吉岡真ーし 浅田昭牟 SUB 描 ARINE TOPOGRAPHY OF THENORTHERN END OF YAP TRENCHt YoIwabuchi*,ShinichiYoshioka*andAkiraAsada* Abstract Hydrographicdepartmentconducted nallowmultibeambathymetricsurveyinthetrenchjunction between the Yap trench and the Mariana trench. The survey area includes the western end of Caroline ridge,the western endof the Marianatrench,and the northern endof the Yap trench. TheYaptrenchhas nosedimentonthetrenchaxisexceptforitsnorthernend.However,several benchin th 巴 waterdepth of 5000m to6800mare recognized on the lower trench slopeof the Yap arc. The Mariana arc also has a bench on its trench slope. The bench of the Mariana arc is composed from NW-SE trending micro ridges and troughs in echelon.This can be explained by the strike slip motion between the Pacific plat 巴andthe Mariana arc. Upper trench slope of the Yap and Mariana arc is simple gradient. However, th 巴Carolineridge is covered with irr 巴 gularups and downs. This feature suggests the geologicaldifference between theCaroline ridgeand the Yap or Mariana ridge. A smallridge locates on thearc junction.The ridge has 30km length and 20km width.The Yaparc and the Marina arc is connected by the ridge. Normal faults are recognized on the back of the ridge. Th 巴 largestfaulthasN20'Wtrend,anddisplacementismorethan1500m.Thesefaultsareevidenceof extension force between theYaparcand the Marianaarc. しはじめに 海上保安庁水路部は,商太平洋共同調査(WESTPAC )の一環として,フィリピン海を縁どる海溝の海底 地形,重力等の調査を行っている. 1988 年及び89 年務査では,ヤッフ。海溝北端部の調査を行った。ここでは, この測量によって明らかにされた,シービームによる海底地形について報告するとともに,地形について若 干の考察を試みる。 2. 調査の概要 調査はいずれも測量船拓洋によって行われた。測深はナローマルチビーム測深機(シービーム)により, 測位はGPS,NNSS ,ロラン C 等からなる複合測立装置により行った。本報告ではふれないが,同時に海上 重力計による重力測量も実施している.調査の概要は次のとおり。 t Received 30th January1990 * 海洋調査謀. Ocean Surv 巴 ysDivision
12
Embed
ヤッブ海溝北端部の海底地形 - MLIT...ridge, the western end of the Mariana trench, and the northern end of the Yap trench. The Yap trench has no sediment on the trench
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
水路部研究報告第26号平成2年 3月30日
REPORT OF HYDROGRAPHIC RESEARCHES No.26 March, 1990.
ヤッブ海溝北端部の海底地形T
岩淵洋*・吉岡真ーし 浅田昭牟
SUB描ARINETOPOGRAPHY OF THE NORTHERN END OF YAP TRENCHt
Yo Iwabuchi*, Shinichi Yoshioka* and Akira Asada*
Abstract
Hydrographic department conducted nallow multi beam bathymetric survey in the trench junction
between the Yap trench and the Mariana trench. The survey area includes the western end of Caroline
ridge, the western end of the Mariana trench, and the northern end of the Yap trench.
The Yap trench has no sediment on the trench axis except for its northern end. However, several
bench in th巴 waterdepth of 5000m to 6800m are recognized on the lower trench slope of the Yap arc.
The Mariana arc also has a bench on its trench slope. The bench of the Mariana arc is composed from
NW-SE trending micro ridges and troughs in echelon. This can be explained by the strike slip motion
between the Pacific plat巴andthe Mariana arc. Upper trench slope of the Yap and Mariana arc is simple
gradient. However, th巴Carolineridge is covered with irr巴gularups and downs. This feature suggests the
geological difference between the Caroline ridge and the Yap or Mariana ridge.
A small ridge locates on the arc junction. The ridge has 30km length and 20km width. The Yap arc
and the Marina arc is connected by the ridge. Normal faults are recognized on the back of the ridge. Th巴
largest fault has N20'W trend, and displacement is more than 1500m. These faults are evidence of
extension force between the Yap arc and the Mariana arc.