Tectonics features in the lower slope domain of the accretionary wedge offshore southwestern Taiwan

• Main Authors: Siou-Min Wun, 溫修敏
• Other Authors: 劉家瑄
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/4c7k8f

碩士 === 國立臺灣大學 === 海洋研究所 === 106 === The accretionary wedge offshore southwestern Taiwan is regarded as an important area to tectonic geology studies. Different structural styles formed by the subduction and arc-continent collision processes can be found in the accretionary wedge. In the past studies, the accretionary wedge has been divided into the lower slope with fold-and-thrust structures and the upper slope with highly deformed structures. Furthermore, the lower slope of the accretionary wedge can be separated into two segments: the frontal segment with blind thrusts and monoclines and the rear segment with outcropping thrusts and symmetrical anticlines. While the distribution of the structures are described well in the larger area, our study aim to observe the geometry of the folds and thrusts in a smaller scale, the evolution of the structures and the distribution of the decollement and the deformation front. In this study, we reprocess and analyze several large-offset multi-channel seismic reflection data collecting by TAICRUST and TAIGER plans in ECHOS software. In addition to the basic seismic data processing, we use SRME and Radon filter to reduce the multiples. Finally we do the prestack depth migration converting time domain into depth domain to get better image in the deeper part of the seismic profile and more accurate information about the angle and geometries of the structures. Based on the thin-skin tectonics and the fault-bend folding, fault-propagation folding and detachment folding models, we find that detachment folds (brittle to ductile stratum) are recognized in the frontal segment while the fault-propagation folds (brittle stratum) are dominant in the rear segment. However, only fault-propagation folds are found in Manila subduction zone while detachment folds can be seen as the evidence of the arc-continent collision in the north of 21°N.