橫移壓縮作用引致黏彈性褶皺生成機制數值模擬初探

Folding of Single Elasto-viscous Layer Formation Caused by Transpression Mechanism-Numerical Simulation

胡啟文(Chi-Wen Hu)

指導教授 ： 鄭富書

共同指導教授 ： 林銘郎(Ming-Lang Lin)

國立臺灣大學/工學院/土木工程學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.01974

摘要

台灣島的新地體構造主要是受到歐亞板塊與菲律賓海板塊的斜聚合導致的蓬萊造山運動所控制，以8.2 cm/yr的速度，朝305-310°的方向移動(Yu et al., 1997)。陳建華(2001)以砂箱物理模型實驗及三維彈性數值模擬分析結果比對至臺東縱谷西部地區及臺灣東南部地區之地表地形與地質構造，此二地區由南往北褶皺構造之型態及空間分佈情形，也與前人研究所述，其板塊碰撞之壓縮位移所佔比例有由往南往北漸增之結果相同(Lu et al., 2002)。
由前人研究中(Yu et al., 1997)，可知菲律賓海板塊以8.2cm/yr的速度向歐亞大陸板塊擠壓，因此對於應變速率對不同橫移壓縮條件下對褶皺產狀之影響為何，為需探討之問題。本研究中藉由Schmalholz & Podladchikov(1999)對黏彈性褶皺行為區分之理論，找出應變速率快或慢之定義。並由三維黏彈性數值模擬之結果來與臺灣東南部之褶皺型態比較，期望能更了解臺灣東南部現生褶皺構造是處於何種應變速率之條件下所生成。
由二維黏彈性材料數值模擬之結果與Schmalholz & Podladchikov (1999)之理論比較，定義出將當時之介質之黏滯係數倒數值來作為進入黏彈性褶皺波長形成受黏性阻抗比影響之應變速率門檻值，來作為所謂應變速率『快』或『慢』之依據：(1)當褶皺發生時之波長受彈性阻抗比所主控時，此時之應變速率是屬於『快』之狀態；(2)當褶皺發生時之波長受黏性阻抗比所主控時，此時之應變速率是屬於『慢』之狀態。
由三維黏彈性材料數值模擬中，以不同應變速率及不同橫移壓縮比例下之模擬結果，菲律賓海板塊擠壓歐亞大陸板塊之作用應該為應變速率為『慢』之情況下，而造成臺灣東南部之地形及地質構造型態。

關鍵字

黏彈性 ； 褶皺 ； 橫移壓縮 ； 應變速率 ； 數值模擬

並列摘要

Neotectonics of Taiwan is mainly controlled by the oblique convergence between the Eurasian plate and the Philippine Sea plate. The convergence velocity has been estimated at 8.2cm/yr in the N54°W direction(Yu et al., 1997). Sandbox and 3-D Finite element model have been used to verify the role of the transpression mechanism in the structures and reconstruct the evolution of the deformation at the southeastern Taiwan and the west of longitudinal valley (Chen, 2001). Lu et al. (2002) observed the increasing proportion of compression of oblique convergence between the Eurasian plate and the Philippine Sea plate from south to north. Chen’s (2001) result was resembled to Lu et al. (2002).
In the past research, the convergence velocity between the Eurasian plate and the Philippine Sea plate has been estimated at 8.2cm/yr in the N54°W direction(Yu et al., 1997), but it’s issue that the influence of fold possession in different strain rate and the proportion of oblique convergence. This research chooses dominant wavelenth ratio method (Schmalholz & Podladchikov, 1999) to distinguish what the strain rate is ‘’fast’’ or ‘’slow’’ in 2D elasto-viscous model. Expect to know the Taiwan Island extruded under ‘’fast’’ or ‘’slow’’ strain rate by 3-D elasto-viscous finite element model.
The comparison of 2-D elasto-viscous finite element model with dominant wavelenth ratio method (Schmalholz & Podladchikov, 1999), the reciprocal value of coefficient of matrix viscosity which equal to the value of strain rate is the threshold to distinguish the fold wavelenth controlled by elastic competence contrast(Re) or viscosity competence contrast (Rv)：(1)When buckling, fold wavelenth is controlled by elastic competence contrast(Re) in so-called ‘’fast’’ strain rate；(2)When buckling, fold wavelenth is controlled by viscosity competence contrast(Re) in so-called ‘’slow’’ strain rate.
In this research, the result of using different strain rate and the proportion of oblique convergence the by 3-D elasto-viscous finite element, the strain rate is so-called ’’slow’’ between the Eurasian plate and the Philippine Sea plate.

並列關鍵字

ABAQUS ； transpression ； fold ； strain rate ； elasto-viscous

參考文獻

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