https://scholars.lib.ntu.edu.tw/handle/123456789/36111
標題: | Slip-rate Estimation of Active Fault by Luminescence Dating on Deformed River Terraces at Tsaotun, Central Taiwan | 作者: | Chen, Ya-Wen | 公開日期: | 21-十一月-2003 | 出版社: | 臺北市:國立臺灣大學地質科學系 | 摘要: | This study carried out optical stimulated luminescence (OSL) ages of the tectonic-disrupted terraces at Tsaotun, where the 1999 earthquake fault (i.e., Chelungpu) runs through. Over there, a number of investigations have been done, but it is still difficult to evaluate the slip-rate and recurrence interval without age control. For the purpose of understanding neotectonic behavior of the Chelungpu fault, the ages of the terraces are imperative to be determined. Radiocarbon dating is unlikely applied in fluvial coarse deposits due to the syndepositional carbonaceous materials are easy to be decomposed. Alternatively, OSL dating is therefore tried on sandy layers intercalated within massive gravel deposits found at Tsaotun. All the terraces developed at Tsaotun are identified as strath terraces, indicating the depositional age is very close to the surface age that is the best constraint in deriving the long-term slip rate of the related active fault. Three samples are collected and presented. In this study only the fraction of coarse quartz, i.e., 90-150 µm, is sieved out and tested by the Single-Aliquot Regenerative (SAR) dose protocol with 36 aliquots for each. Considering the incomplete bleaching during quick deposition, the OSL/TL and OSL/OSL ratios are applied to normalization in each aliquot and to approach the true De. Dose rate is derived by ICP-MS and XRF analyses. For confirmation of the residual luminescence signals in the fluvial sediment, the modern samples collected in Wuhsi were also measured using the same protocol. Based on the results of modern samples, we found that the residuals are inevitable in younger samples, especially in the river reach where debris flow is dominant. On the contrary, the samples older than 10 ka will be slightly influenced because the age error covers the residual uncertainty. The OSL age of the terrace samples in the hanging wall is dated ca. 24 ka, which has been corrected for poorly-bleaching problem. Comparing to the ages collected down hole in the footwalls, we found out vertical displacements of ca. 72 m and 43 m, has been cumulated by the slips of main and back thrust. Thus, the long-term slip rates of the main and back thrust are 2.7-3.3 m/ka and 1.8-2.2 m/ka, respectively. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/20060927121706195384 | 其他識別: | 20060927121706195384 |
顯示於: | 地質科學系 |
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