桃園臺地群地表變形與地下構造之研究

Surface Deformation and Subsurface Structure of the Southern Taoyuan Tablelands, Northwestern Taiwan.

張育仁(Yu-Jen Chang)

指導教授 ： 張中白

國立中央大學/地球科學學院/地球物理研究所/碩士(2008年)

摘要

臺灣島由於板塊運動方向與邊界的幾何關係，主要之地形為南北向的構造線和山脊，然而在臺灣西北部，由於觀音高區的存在，卻造成一系列近東西向的構造於此地區發育，湖口斷層便為一例，而此些構造周圍的地區便深受構造之活動行為影響與控制。另一方面，位於臺灣西北部的桃園臺地群為人口相當稠密的區域，緊鄰在構造周遭的人口密集都市區與工業區便成為了地質災害潛勢區域。因此，詳細研究並了解此區域的構造活動與地表變形行為顯得格外重要。近年來衛星遙測技術日益精進，利用雷達干涉技術對於測量大範圍、面狀的地表變形更有效率。本研究應用合成孔徑雷達差分干涉技術來觀測地質災害潛勢區域桃園南部臺地群近期的地表變形行為，並配合大地應變場分析、礫石破裂軸古應力分析以及斷層活動模擬地表變形，試圖了解研究區域現今的地表變形與構造活動之間的關聯性，以期達到減輕地質災害之目的。研究結果顯示桃園南部臺地群地區南方的古應力來向大約位於111°至141°之間。而臺地群近期差分干涉結果顯示的地表變形行為，中壢與楊梅地區為持續下陷的狀況，位於湖口斷層附近的變形並不明顯，平鎮地區存在著抬升變形中心，與傳統精密水準測量的結果十分吻合。應變率場研究結果顯示研究區域呈現西北—東南的微量壓縮應變型態，且湖口斷層周遭仍有較周圍高之應變強度。本研究更進一步建立一地下構造模型進行斷層活動模擬與雷達差分干涉相互對照的結果，推測平鎮背斜與雙連坡線形之下可能存在一活動較快之小型逆移斷層，且湖口斷層近期以緩慢速率活動且影響著桃園南部臺地群的地表變形。

關鍵字

地表變形 ； 雷達差分干涉 ； 桃園南部臺地群 ； 應變率 ； 應力 ； 斷層活動模擬

並列摘要

The main topography in Taiwan Island is tipical structure and ranges with a N—S strike because of the direction of plate movement and the geometry of plate boundary. In addition, The existence of Kuanyin High causes a series of structures with a E—W strike developing in northwestern Taiwan and dominating the deformation of entire area, such as Hukou fault. Besides, since southern Taoyuan Tablelands area is one of the most populated area in northwestern Taiwan, the tectonic activity and the potential geological hazard of this area is an important issue for Taiwan. The Hukou fault in southern Taoyaun Tablelands is evaluated as one of the major and active structures in northwestern Taiwan, along which some industrial parks and communities are well developed. In order to realize the interaction between surface deformation behavior and subsurface structure of this area, we mainly apply DInSAR-technique to engage this study, and cooperate strain rate field analysis, pebble-frature paleostress analysis, and simulated surface deformation from fault model. The interferometric results reveal that the Pingchen area has a few local deformation center, but the surface deformation patterns is not clear to observe in the vicinity of the fault zone. However, the result of pebble-frature paleostress analysis and strain rate field analysis indicate that study area is under a NW-SE stress field(111°~141°) and has slightly obvious strain strength along Hukou fault.Otherwise, we construct a subsurface structure including four faults with distinct dip, and simulate the surface deformation by giving various slip rates. Unexpectedly, the optimum result is well consist with the DInSAR result. The result implies that Hukou is still active with a subtle slip rate around 0.5 cm/yr and influence the suface deformation behavior of southern Taoyuan Tablelands in recent day.

並列關鍵字

subsurface structure ； surface deformation ； southern Taoyuan Tablelands ； stress ； and fault model. ； strain rate field ； DInSAR

參考文獻

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