https://scholars.lib.ntu.edu.tw/handle/123456789/37156
標題: | 台灣及鄰近地區隱沒與碰撞作用─(子計畫六)台灣及鄰近地區之變形模式(Ⅱ) | 其他標題: | Deformation Mechanism of Collision Mountain Belt around Taiwan (II) | 作者: | 盧佳遇 | 關鍵字: | 地質模型;物理模型;數值模擬;台灣附 近區域;地體架構;地震;應變能;Geological modeling;physical modeling;western Taiwan;earthquakes;tectonics | 公開日期: | 1999 | 出版社: | 臺北市:國立臺灣大學地質科學系暨研究所 | 摘要: | 地質模型為地質學研究中一新的途徑。透過 物理模型及數值模擬,可以輔助我們瞭解大地構造 的可能模式,進而解釋複雜的地質現象。本論文嘗 試進行砂箱模擬實驗可行性的評估,並分析物理模 型中的各邊界條件和主要控制變因對物理模型結 果的影響,再進一步運用砂箱物理模型和三維數值 模型來模擬台灣附近區域地體架構、斜向聚合及基 盤高區對西部區域整體構造的發育、演化及構造間 相互關係的影響,以期能對台灣地區大區域構造能有些許的了解與助益。本研究模擬砂箱行為,獲得以下幾點結論: 大部分的模擬,都發育整組的共軛逆斷層,並形成 衝起構造;且大部份同一組共軛逆斷層的發育,都 是逆斷層早於背衝逆斷層。後阻體(backstop ) 的摩擦係數對模擬結果有很大的影響,隨著摩擦係 數的減小,會使應變集中於後阻體上方,並沿著後 阻體斜坡往上爬。後阻體傾角的增大,應變越容易 往前傳遞;傾角減小會使應變集中於後阻體的底部 部份,並沿著基腳發育一組衝起構造。隨底部摩擦 係數的減小,應變容易往前傳遞。材料的軟硬度對 位移的傳遞雖有影響,但影響的程度不如其他因素所影響的程度大。本研究探討西部基盤高區對鄰近新構造運 動的影響,歸納結論如下:後阻體最主要的影響在 於斜向聚合活動的早期;後期構造的外型與發育, 則受控於基盤外型和後阻體嵌入所造成的早中期 構造,所以中部地區,變形前緣往前移,基盤高區 前方因基盤的阻擋效應,致使變形前緣往前發育得 較慢,而停留於高區前方,南部區域因無高區阻擋 且岩層變厚,易使變形前緣往前移,綜合以上原因即為台灣西部區域存在著S 型變形前緣的可能原 因。大部分的逆斷層為有秩序的往前發育,越向西 越晚發育。台灣西部之大度台地、八卦台地、恆春 西台地可能因逆斷層作用而形成而,屏東谷地、台 中盆地、恆春平原等可能為一馱背式盆地。從本實 驗的初步成果可以印證,砂箱物理模型為一可以繼 續發展的工具,尤其對於構造的發育演化,展現了 無窮的潛力。從三維數值模型的參數分析中,建議 基盤高區的界面摩擦角小於15 ° 。數值模型中基盤 高區的存在,會造鄰近區域應力場、應變場方向的 偏轉。從斷層性質的探討中,建議基盤斜坡附近斷 層在早期傾向於發育逆斷層,中晚期則轉換成發育 平移斷層。嘉南麓山帶前緣附近地區為應變能集中 的區域,應小心地震發生,並作好防災的準備。 Geological modeling is a new way in geological studies. By the help of physical modeling and numerical modeling, we can understand the possible models of the development of the kinematics and dynamics evolution of structure. These studies try to estimate the possibility of sandbox simulation experiments in physical modeling; and try to analyze the effect of boundary conditions and main controlling factors in physical modeling. Furthermore, by using physical modeling and three-dimensional numerical modeling, we try to simulate the consequence of geological settings, oblique convergence and basement high in the inter-relationship between the development, evolution and structure in the western Taiwan. We hope that will help us understand more about the regional tectonics of Taiwan. By the simulation of sandbox behavior, there are some conclusions: most models develop conjugate thrust faults and pup-up structures; in most cases, the same set of conjugate thrust faults developed earlier than the backthrust faults. The modeling result is highly affected by the friction coefficient of backstop; as the friction coefficient reduced, the strain would concentrate on the top part of the backstop and increase along the ramp of the backstop. The greater the angle of inclination of the backstop, the easier the forward propagation of the strain. Reduction in the angle of inclination results in the concentration of strain near the toe front of the backstop, and a set of pup-up structures could be found at the toe of the backstop. As the friction coefficient of the base reduced, the forward propagation of the strain becomes more easily. Thought the competence of materials would affect the displacement of the propagation, it is not as important as the others factors. This research aimed to realize the effect of the basement high of western Taiwan during oblique convergence. Results: Backstop mainly affects the earlier stage of the oblique convergence; the shape of the basement and the early stage structures formed by the indent backstop controls the shape and development of later stage structures. As a consequence, forward propagation of the deformation front occurred in the central western Taiwan, because of the resistance at the front of the basement high, the deformation front propagated slowly at the front of the basement high. There is low resistance in the southern Taiwan and the sediments there are thickened, the deformation front moved forward. The above reasons may explain the S-shaped deformation front at the western Taiwan. Most thrust faults are forward-breaking sequence and it develops later in the western region. The formation of Tatu terrace, Bakua terrace, west Hengchun terrace may be the result of thrust faults; Pingtung valley, Taichung basin, Hengchun plain may be piggy-back basins. And these results are supported by the preliminary results of these experiments. Sandbox physical modeling is very useful in the research of the development and evolution of geological structures, and it showed great potential in this research. From the analysis of the parameters of the three-dimensional numerical modeling, we suggest that the interface friction angle of the basement high should be smaller than 15°. The existence of the basement high in the numerical modeling results in the change in the direction of stress field and strain field. Based on the nature of faults, we suggest that the faults near basement ramp tend to develop thrust faults and strike-slip faults would develop at later stage. Since the strain energy concentrated at the front of the West-Foothill near Chiayi and Tainan, these areas may affect by earthquakes. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/11722 | 其他識別: | 882116M002018 | Rights: | 國立臺灣大學地質科學系暨研究所 |
顯示於: | 地質科學系 |
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