Landforms of the Izu-Ogasawara Trench by the narrow multi beam echo sounder.
The narrow multi-beam bathymetric survey in the Izu-Ogasawara Trench conducted by the survey vessel ”Takuyo”of Hydrographic Department of Japan. The survey area is from 27。30’N to 32°-20' N and about 45 km wide along trench axis. The Izu-Ogasawara Trench extends in N-S direction along the east of the Izu-Ogasawara Arc, and is situated on the boundary between the Philippine Sea Plate and the Pacific Plate. The trench is subdivided into three major geomorphological units as follows : 1) the landward wall of the trench, 2) the trench floor, 3) the seaward wall of the trench which are arranged from west to east. On the landward wall of the trench,many gentle slopes originated from submarine landslides are recognized. The size of landslides in the southern part of the trench become more large scale than those in the northern part. In the southern end of the survey area, there is a gigantic landslide which moves the landward wall of the trench to east and narrows the trench floor. The trench floor is separated into several basins by the ridges which extend in the NNW-SSE direction. On the central trench floor, there is a subducting seamount which is deforming by normal fault. The seaward wall of the trench has many horsts and grabens which formed by normal faults. The normal faults are subdivided into two types as follows . 1) faults with the strikes parallel to the trench axis, 2) faults with the strikes oblique to the trench axis. The parallel faults are formed by the bend of the oceanic plate (the Pacific Plate) which is subducting beneath the Philippine Sea Plate. In the southern part, the oblique faults is more well distributed than those in the northern part. The strike (NW-SE) of the oblique faults correspond to that of the faults of the fracture zone : the Bosδ Fracture Zone, the Ogasawara Fracture Zone on the western part of the Pacific Plate. The fact supports the idea that the plate bending also forms oblique faults which make use of the lineament of the fracture zones.
| Main Authors: | , , |
|---|---|
| Format: | Journal Contribution biblioteca |
| Language: | Japanese |
| Published: |
1991
|
| Online Access: | http://hdl.handle.net/1834/16095 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|