斷層在大地震震後的滑移型態可反應斷層摩擦特性，進而瞭解其破裂過程及發震機制。2003年12月10日成功地震規模Mw 6.8，震央位置接近台東縣成功鎮，此地震起因於池上斷層的錯動破裂。由地震分佈發現，池上斷層是一高角度的逆衝斷層，同時具有快速潛移及發生地震的行為。本研究使用台灣東部11個GPS連續觀測站的資料，利用Bernese 4.2軟體計算各測站的精確座標，求得測站相對於澎湖白沙（S01R）在成功地震震後5個月的地表位移。藉此研究成功地震之震後滑移，以瞭解池上斷層的摩擦特性。5個月地表最大震後水平位移為85.8 mm，最大垂直位移為 83.7 mm。利用三維彈性錯位模型（3D elastic dislocation model）反演震後的地表位移，得到斷層面上的震後滑移分佈。結果發現滑移量主要集中在沿斷層面的震源上方淺部0-8 km的部分，其震後滑移的最大量為641 mm位於深度4公里，所產生的地震矩（moment）為0.85×1026 dyne-cm，此值遠大於餘震所產生的4.69×1024 dyne-cm，由此顯示震後滑移主要是無震方式在釋放能量。利用三維彈性錯位模型計算同震滑移的分佈，再使用摩擦組成模型（rate-and-state friction model）估算震後滑移的分佈以及斷層σ（a-b）值（σ為正應力，a、b為摩擦係數，當a-b為正值時，斷層為速度強化，以潛移為主），瞭解斷層的特性。研究發現同震滑移的分佈必須是相當緊密（compact）的，才可產生劇烈的同震應力變化，使地表在短時間內產生大的震後位移。在σ（a-b）的分佈上，顯示斷層北段的σ（a-b）較大，為穩定滑動的區域；斷層淺部存在一個σ（a-b）值非常低的區域，使震後滑移集中在淺部，而同震地表破裂的位置受控於近地表σ（a-b）值的分佈。在同震應力增加的區域，σ（a-b）值趨近於0時會產生破裂；而當σ（a-b）值較大時，即便應力增加，破裂也不會發生。

Postseismic slip from large earthquake often reflects frictional properties of the fault zone. Frictional properties of fault can be used to understand the rupture process and the earthquake mechanism. The Chengkung earthquake of magnitude Mw 6.8 occurred in eastern Taiwan on December 10th 2003, resulting from rupture of the Chihshang fault. According to the distribution of the earthquakes, the Chihshang fault is a high-angle reverse fault. It is rapidly creeping and capable of producing large earthquake. We used 11 continuous Global Positioning System （CGPS） data and Bernese software v4.2 to obtain the precise station coordinates relative to Paisha, Penghu in the period of 5 months after the Chengkung earthquake. The largest horizontal and vertical postseismic displacements are 85.8 and 83.7 mm, respectively. This research is to understand the frictional properties of the Chihshang fault by analysing postseismic slip of the Chengkung earthquake.
Afterslip was determined by inverting CGPS data using 3D elastic dislocation model. The results showed that the slip was focused on shallow part of fault （0 - 8 km）. The maximum afterslip is 641 mm at the depth of 4 km. The geodetic moment is 0.85×1026 dyne-cm which is far greater than aftershock which is 4.69×1024 dyne-cm, indicating that afterslip occurred aseismically. We estimate coseismic slip by 3D elastic dislocation model, and estimate afterslip and σ（a - b） （σ is normal stress; a and b are frictional parameters） by rate-and-state friction model. We found that the coseismic slip distribution must be quite compact in order to generate a stress perturbation which is large enough to generate the rapid afterslip. According the distribution of σ（a - b）, the value of σ（a - b） at north part of the Chihshang fault is large, indicating this section is stable sliding. The small value of σ（a - b） on the shallow part of the fault, and the lateral heterogeneity in frictional parameters result in a localization of afterslip. The results correlated well between two models. The areas of the coseismic surface rupture are controlled by the distribution of σ（a - b） near surface. In the stress increase region, the rupture will be occurred on the area with σ（a - b） value close to zero but not on the area with large σ（a - b）.

中文部分
何春蓀，臺灣地質概論-臺灣地質圖說明書，經濟部中央地質調查所，中華民國，共164頁，民86。
李建成、朱傚祖、安朔葉、胡植慶、余水倍、陳宏宇、鄭富書、林正洪、饒瑞鈞、周錦德、張勝雄和姜國彰，從地殼變形與斷層活動討論地震災害潛在性：花東縱谷池上活斷層的研究，地質，21卷，第二期，第31到52頁，2002。
蔡旻穎、饒瑞鈞，從台灣內政部GPS連續追蹤站探討1999年Mw 7.6集集地震前後之遠場地殼變形，九十四年度地球物理學會年會暨蔡義本教授榮退專題研討會摘要集，中央研究院，第106頁，2005。

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