Preliminary study of marine topographic characteristics around western and southern Hengchun penisula
Date Issued
2008
Date
2008
Author(s)
Kao, Pu-Sheng
Abstract
This research tries to access and understand the sea area around Hengchun west and south tablelands, including Nan-Wan, Hai-Kou and Hengchun west tableland. In the area above, there are few data of its underwater landform, and are in a low resolution to do further analysis. By means of using high definition Multibeam survey system (MBS), Sidescan sonar system (SSS) and 3.5KHz subbottom profiler (SBP), this research tests and gathers more data of this area''s underwater landform and bedding status, then evaluates and judges the causes and effects of its millimetric landform, bedding changes and the structure. The major purposes of this research are as follows: At the first place the research tries to gather more specific information of Hengchun fault, in lack of a clear position of its fault line, researchers were not able to define the ways and forms Hengchun fault performs. By studying the extended sea area of Hengchun fault, to go further into its extension area and the acting forms. Through the data collected from Nan-Wan underwater landform, Hengchun fault and its extension can be observed in 85 meters underwater. Besides that, the research finds that the east side valley of Nan-Wan outer sea has the same moving direction as the landform of the Nan-Wan research area, and is as the way Hengchun fault shows. Therefore it is likely that Hengchun fault extends into the sea in either this area or in the twister in isobath. The research does not find obvious trace or route Hengchun fault made in close-shore area of Nan-Wan through SSS. The research also finds that there is a likely submarine landslide landform in outer Hai-Kou in the north side of west tableland. However, the location and forming is different from other landslide landforms. There is similar landform as stated above in the end of a thrust fault in outer sea area in north Taiwan. These show that the moving of Hengchun ground fault only extends until outer sea of Hai-Kou to from this kind of landform. Thus the research may suggest that Hengchun fault may not be connected with Chow-Chou fault, or even they are connected, the fault forming also stops in this place. The second part of this research is trying to clarify and explain the major factors causing the lifting of Hengchun west tableland. Former researchers advise that measurement shows that both east and west sides of the tableland are lifting, which indicating that under the tableland there is one other major thrust fault growing, and it is located in the west coast outer sea in Hengchun west tableland. From the landform of west tableland and the features of Hongtsai canyon, it is likely that the west coast fault is located in upper Hongtsai canyon. In the north of lower Hongtsai canyon, the research finds an opening towards to the south west landform, from the profile the research suggests the landform as a stretching structure line. The research also finds that in the southern Hongtsai Ridge of lower Hongtsai canyon, there is a series of landform which opens towards to south west. The above landform is considered extremely similar to the one in north. In short, the research would suggest that the lining landform in north and south Hongtsai canyon could be caused by the fauly in west coast thrusting into Hengchun west tableland or the seperation of the fold axis. These lining landforms are both caused by the seperation.
Subjects
Hengchun fault
Hongtsai canyon
Hongtsai ridge
Multibeam
Sidescan
3.5KHz subbottom profiler
SDGs
Type
thesis
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