Neotectonics in the southernmost part of Longitudinal Valley, eastern Taiwan and it’s implications to the activity of the Lichi fault and the Luyeh fault

• Main Authors: Chuan-Yao Chi, 紀權窅
• Other Authors: Wen-Shan Chen
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/06370956735192859170

碩士 === 國立臺灣大學 === 地質科學研究所 === 95 === In order to fully understand the neotectonics in the southernmost part of Longitudinal Valley, eastern Taiwan, we mapped the geology and surveyed the fault traces and terraces in Longitudinal Valley from Juiyuen to Taitung city. In this study we distinguished a new formation, Chulu Gravel, from Pinanshan Conglomerate based on its gravel lithology, sedimentary character and spatial relationships between two formations. In fault traces survey, we found that slip along Lichi fault has stopped in some area and inferred the recent faulting probably branches to the west. This branch fault may propagate into Pinanshan Conglomerate and its trace should be in the Peinantahsi river. Luyeh fault deformed the lateritic and Holocene terraces and fault tip didn’t cut through surface. In Shinlian area, the faults caused the uplifting of terraces and formed three obvious scarps. It is observed the Lichi Fm. thrust on terrace gravels in outcrop, and the rupturing of the artificial structure may represent the fault is creeping. All the features of the faults in Shinlian area are similar to Chishang fault, so we classified the faults in this area as Chishang fault.Based on the dating of the terraces we estimate the vertical deformation rate of the Luyeh fault is about 3 mm/yr, and the Lichi fault is about 17-20 mm/yr. Analysis of the pattern of GPS velocity field, we inferred the Lichi fault and the Luyeh fault behave as creeping thrust faults.