臺灣西北部在更新世以後受歐亞板塊與菲律賓海板塊斜向碰撞影響，形成本區內正斷層構造反轉為逆斷層與橫移斷層兼具之構造型式。其中，白沙屯構造位於臺灣西北部苗栗地區外麓山帶前緣，受龍港斷層向西北逆衝上拱而形成一不對稱背斜構造。本研究根據一系列網狀的時間轉換深度一比一的震測剖面與井下地質資料建立臺灣西北部苗栗地區白沙屯反轉構造地下三維構造形貌，根據理論模型建立斷層相關褶皺演化模型，最後根據斷層面分析檢視該反轉構造的斷層封閉特性。
由一系列震測解釋結果顯示，白沙屯構造位於兩同傾向的東西向斷層之間，龍港斷層東段為東西走向，向西段轉為東北-西南走向，其呈現高傾角(東南傾約52度)，白沙屯背斜構造即為龍港斷層向西北逆衝上拱擠壓而形成，深部地層落差較大，淺部地層落差較小，推測龍港斷層所產生的構造為斷層延展褶皺(simple step)。由頂部構造圖顯示，白沙屯構造淺部有東構造高區與西構造高區，往下二構造高區逐漸分離，東構造高區逐漸消失，西構造高區仍存在但規模亦逐漸變小，此結果推測與斷層傾角與滑移量變化有關，當斷層傾角變陡且滑移量變小，褶皺形貌受上拱影響變形程度增大
；在側向變化上來看，西構造高區褶皺形貌變形程度變化不大，東構造高區褶皺變形程度向上增大，推測因東構造高區與西構造高區間分隔的鞍部為正斷層構造形式。由三角剪切模型模擬結果顯示，龍港斷層在白沙屯構造為高角度滑移向西北逆衝而上之逆衝斷層，其滑移作用可以形成與震測剖面所解釋的背斜構造相似之構造，而構造變形量或潛在破裂面密度集中在淺部的背斜構造且靠近龍港斷層上盤的位置。由亞倫斷層面圖進行斷層面分析顯示，龍港斷層在斷層東側從東西走向往西側轉為東北-西南走向，斷層滑移量最大值應於斷層轉折處附近，其次西側，最小在東側，斷層淺部上下盤地層落差較深部小。

SUMMARY
Inversion tectonics is a complex structural style arising from different periods in the same structures. Generation of an inversion tectonics relates to change of a regional stress field. For example, an basin with syn-rift sequences, which develops originally by extensional structures within extensional stress field, may undergoes compressional stress field later, then compressional structures will form and overlay in the hanging wall of the extensional fault zone to form a “positive structural inversion”. In this study, we used a grid of seismic sections and well bore data to reconstruct a three-dimensional geometry of the folds and convert the time sections into depth sections of identical V/H scale to build the Paishatun inversion structure in the Miaoli area. We also established a three-dimensional structural model according to fault-related folding theories. Finally, we constructed the Allan map to examine our fault sealing.
According to the interpretation of a series of seismic profiles, the Paishatun Anticline located between two E-W striking reverse faults that dip to the same direction. The eastern part of the Lungkang Fault was E-W striking and the western part of the Lungkang Fault changed into NE-SW striking and tranformed a high-angle thrust. Structure contour map shows the structure top-down on the top of each strata in the Paishatun area. The Lungkang Fault previously was a normal fault and then reactivated into a thrust fault. Trishear model shows that the Paishatun Anticline formed by the Lungkang Fault as a fault propagation fold (simple step) and consistent with the inversion structure in interpretated seismic profiles. The Allan map shows that the largest fault throw occured at the turning point of the Lungkang Fault, followed by the western section, and the smallest throw in the eastern section.
Keywords: Thrust, the Paishatun Anticline, Inversion Tectonics, Fault Trap

INTRODUCTION
Inversion tectonics is a complex structural style arising from different periods in the same structure. Generation of an inversion tectonics relates to change of a regional stress field. For example,an basin with syn-rift sequences, which develops originally by extensional structures within extensional stress field, may undergoes compressional stress field later, then compressional structures will form and overlay in the hanging wall of the extensional fault zone to form a “positive structural inversion”.

METHODS
In this study, we used a grid of seismic sections and well bore data to reconstruct a three-dimensional geometry of the folds and convert the time sections into depth sections of identical V/H scale to build the Paishatun inversion structure in the Miaoli area. We also established a three-dimensional structural model according to fault-related folding theories. Finally, we constructed the Allan map to examine our fault sealing.

RESULTS and DISCUSSIONS
According to the interpretation of a series of seismic profiles, the Paishatun Anticline located between two E-W striking reverse faults that dip to the same direction. The eastern part of the Lungkang Fault strikes E-W and the western part of the Lungkang Fault changed into NE-SW striking and transfomed into a high-angle thrust.

Structure contour map shows the structure top-down on the top of each strata in the Paishatun area. The Lungkang Fault previously was a normal fault and then reactivated into a thrust fault. The eastern part of the Lunkang Fault might formed a fault propagation fold and changed to a fault bend fold in the western part of the Lunkang Fault.

Trishear model shows that the Paishatun Anticline formed by the Lungkang Fault as a fault propagation fold (simple step) and consistent with the inversion structure in interpretated seismic profiles.

The Allan map shows that the largest fault throwoccurs at the turning point of the Lungkang Fault, followed by the western section, and the smallest throw in the eastern section.

CONCLUSIONS
1. According to the interpretation of a series of seismic profiles, the Paishatun Anticline located between two E-W striking reverse faults that dip to the same direction. The eastern part of the Lungkang Fault striked E-W and the western part of the Lungkang Fault changed into NE-SW striking and transfomed into a high-angle thrust.
2. Structure contour map shows the structure top-down on the top of each strata in the Paishatun area. The Lungkang Fault previously was a normal fault and then reactivated into a thrust fault. The eastern part of the Lunkang Fault might formed a fault propagation fold and changed to a fault bend fold in the western part of the Lunkang Fault.
3. Trishear model shows that the Paishatun Anticline formed by the Lungkang Fault as a fault propagation fold (simple step) and consistent with the inversion structure in interpretated seismic profiles.
4. The Allan map shows that the largest fault throwoccured at the turning point of the Lungkang Fault, followed by in the western section, and the smallest throw in the eastern section.

參考文獻
中文部分
何春蓀，2006，二版，台灣地質概論：台灣地質圖說明書，經濟部中央地質調查所。
何春蓀，1982，台灣地體構造的演變─台灣地體構造圖說明書：中華民國經濟部，110頁。
何信昌，1994，台灣地質圖說明書─苗栗：經濟部中央地質調查所，第十二號，69頁。
張憲卿，1990，台灣地質圖說明書─白沙屯：經濟部中央地質調查所，第十一號，29頁。
謝凱旋、張徽正、黃敦友、何信昌、林偉雄、林啟文、陳華玟，2003，台灣地層對比表：經濟部中央地質調查所。
中國石油公司，1994，台灣西部地質圖，苗栗圖幅（1:100000），中國石油公司台灣油礦探勘總務編印。
陳培源，2006，台灣地質，台灣省應用地質技師公會，共500頁。
楊耿明、吳榮章、丁信修、王佳彬，1994，竹苗麓山帶地下地質構造與油氣儲集：探採研究彙報，第十七期，24-53 頁。
英文部分
Allan, U. S., 1989, Model for hydrocarbon migration and entrapment: AAPG Bulletin, v. 73, p.803-811.
Allmendinger, R. W., 1998, Inverse and forward numerical modeling of trishear fault-propagation folds: Tectonics, v. 17, p. 640-656.
Bailey, R. J., and Stoneley, R., 1981, Petroleum:entrapment and conclusions. in: Tarling, D. H. (ed.), Economic Geology and Geotectonics,Blackwell Scientific,Oxford, p.73-94.
Erslev, E. A., 1991, Trishear fault-propagation folding: Geology, v. 19, p. 617-620.
Fossen H., 2010, Structural Geology, Cambridge University Press, 480p
Groshong Jr., 2006, 3-D Structural Geology, Springer, 400p.
Letouzey, J., 1990, Fault reactivation, inversion and fold-thrust belt, in Letouzey, J., (ed.), Petroleum and Tectonics in Mobile Belts: Technip, Pairs, p.101-127.
Lin, A. T., & Watts, A. B., 2002, Origin of the West Taiwan basin by orogenic loading and flexure of a rifted continental margin: Journal of Geophysical Research, v.107,p.2-19
Mitra, S., 1993, Geometry and kinematic evolution of inversion structures, Amer.Assoc.Petrol. Geol. Bull., v. 77, no. 7, p. 1159-1191.
Namson, J., 1981, Structure of the western foothills belts, Miaoli-Hsinchu Area, Taiwan: (I) southern part, Petrol. Geol. Taiwan, no. 18, p. 31-51.
Namson, J., 1983, Structure of the western foothills belts, Miaoli-HsinchuArea, Taiwan: (II) central part, Petrol. Geol. Taiwan, no. 19, p. 51-76.
Namson, J., 1984, Structure of the western foothills belts, Miaoli-Hsinchu Area, Taiwan: (III) northern part, Petrol. Geol. Taiwan, no. 20, p. 35-52.
Shaw, J. H., Connors, C. D., and Suppe, J., 2005, Seismic Interpretation of Contractional Fault-related folds: AAPG Studies in Geology #53, 156p.
Sun, S. C., 1982, The tertiary basins of offshore Taiwan: Proc. Second ASCOPEConference and Exhibition, p. 125-135.
Suppe, J., 1983, Geometry and kinematics of fault-bend folding: Am. J. Sci., v.283, p.684-721.
Suppe, J., 1984, Seismic interpretation of the compressively reactivated normal fault near Hsinchu, Western Taiwan: Petrol. Geol. Taiwan, no. 20, p. 85-96.
Suppe, J., 1983, Geometry and kinematics of fault-bend folding: Am. J. Sci., v. 283,p. 684-721.
Williams, G. D., Powell, C. M., and Cooper, M. A., 1989, Geometry and kinematics of inversion tectonics, in M. A. Cooper and G. D. Williams,eds., Inversion tectonics: Geological Society Special Publication No. 44,p. 3-15.
Yang, K. M., Huang, S. T., Wu, J. C., Ting, H. H., and Mei, W. W., 2006 , Review and New Insights on Foreland Tectonics in Western Taiwan: International Journal of Geology, v. 48, p. 910-941.
Yang, K. M., Ting, H. H., Wu, J. C., and Chi, W. R., 1997, Geological model forcomplex structures and its implications for hydrocarbon exploration innorthwestern Taiwan: Petrol. Geol. Taiwan, no. 31, p. 1-42.
Yang, K. M., Wu, J. C., Wickham, J. S., Ting, H. H., Wang, J. B., and Chi, W. R., 1996, Tranverse structures in Hsinchu and Miaoli areas: Structural modeand evolution in foothills belt, Northwestern Taiwan: Petrol. Geol.Taiwan, no. 30, p. 111-150.
Yang, K. M., Wu, J. C., Ting, H. H., Wang, J. B., Chi, W. R., and Kuo, C. L., 1994,Sequential deformation in foothills belt, Hsinchu and Miaoliareas:Implications in hydrocarbon accumulation: Petrol. Geol. Taiwan, no. 29,p. 47-74.
Zehnder, A. T., Allmendinger, R. W., 2000, Velocity field for the trishearmodel:Journal of Structural Geology, v. 22, p. 1009-1014.