碩士 / 國立中央大學 / 應用地質研究所 / 87 / In order to insight the detail geological structures in South Okinawa Trough, located in the back-arc region of the Ryukyu Trench system, the reflection seismic profiles in the offshore of NE Taiwan are collected.
Through seismic sequence analysis, three main sequence boundaries are identified, and divide the late Cenozoic deposits of the basin into four sequences namely the basement, S1, S2, and S3 in ascending order. The basement is folded or reflection-free. The reflection configuration of S1 is divergent and indicates the rifting stage. The reflection configuration of S2 is parallel and indicats the post-rift stage. The reflection configuration of S3 is divergent and indicates another rifting stage.
According to the difference in structural pattern, South Okinawa Trough can be divided into four areas namely northern half-graben area, main basin area, horst or high area, and southern half-graben area from north to south.
Normal faults in the northern half-graben area are collateral and dipping southward. Dip directions of normal faults in the main basin area are either southward or northward. Most faults in this area became unactive in sequence S2 and S3. In horst area normal faults have been acting up to now. Normal faults in the southern half-graben are dipping northward.
According to the difference of sequence thickness between hanging wall and footwall, we can tell if the fault is active during the formation of the sequence. So we can divide the normal faults into two group. One group acted during the first rifting stage, and S1 is the syn-rifting sequence. The other group acted during the second rifting stage, and S3 is the syn-rifting sequence.
The first rifting stage started in Late Pliocene. The rifting center located in nothern half-graben area and main basin area. The rifting direction is N155o. The second rifting stage may start in 0.1Ma. The rifting direction is N170o. The rifting center is in the south of 25oN and the east of 122o45''E. The rifting center has moved southward and eastward from first rifting stage to second rifting stage. The tension force has moved 20 degrees clockwise.
| Identifer | oai:union.ndltd.org:TW/087NCU00503003 |
| Date | January 1999 |
| Creators | Buo-Hua Hsu, 徐泊樺 |
| Contributors | Louis L. Tsai, Louis S. Teng, 蔡龍珆, 鄧屬予 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 60 |
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