碩士 / 國立臺灣大學 / 海洋研究所 / 96 / Submarine landslide is one of the mechanisms for sediment transport, and may cause geohazard. However, due to lack of high-resolution bathymetric data, few studies have been conducted on submarine landslides offshore Taiwan.
Taiwan is located in a tectonically highly active area, large quantities of sediment have been rapidly accumulated on the seafloor, and large amount of gas hydrates have been found in the offshore area of southern Taiwan. Thus, the geological condition is suitable for the development of submarine landslide.
In this study, we use GIS (Geographic Information System) software to identify submarine landslides in an area between 21.5˚N and 23˚N, and from 119.3˚ E to 121.5˚E, offshore SE and SW Taiwan, based on seafloor morphology derived from multi-beam bathymetric and SeaMARC II side-scan sonar data. Typical geomorphologic features of a submarine landslide consist of an arcuate headscarp, two sub-parallel sidewalls, and sometimes with slumped material appear at the base of the landslide scar. We also categorize landslides into three different types based on their morphology and the rheology of the sediments. Landslide types 1 and 3 are both consisted of cohesive material, and type 2 might represent less cohesive material comparing to types 1 and 3.
Based on our investigation, the total number of submarine landslides identified is 72, and the sizes of the identified landslides range from 1.3 km2 to 57.5 km2. The total volume of the landslides is 85.01 km3, and the average volume of the landslides is 1.18 km3. These results seem to suggest that landslides may not play an important role for sediment transport in the study area.
The statistic data also show that most frequently observed submarine landslide belong to type 2 submarine landslide, that is, the non-cohesive submarine landslide type, which suggests that submarine landslides in southern offshore Taiwan might occur more easily in less cohesive sedimentary strata.
We also observe that most of the submarine landslides in SW offshore Taiwan are located on the sidewalls of submarine canyons, the arrangements appear to be highly controlled by the structural trends. The triggering mechanisms for submarine landslide might be periodic slope-clearing landslides and gas hydrate dissociation.
In SE offshore Taiwan, the distribution of submarine landslides is controlled by the slope gradients, the steepen slope area present more submarine landslides. The triggering mechanism in this area could be frequent earthquakes or tremors.
| Identifer | oai:union.ndltd.org:TW/096NTU05274006 |
| Date | January 2008 |
| Creators | Chia-Yu Wu, 吳佳瑜 |
| Contributors | 劉家瑄 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 84 |
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