摘要 Abstract：

地震與崩塌皆為地表上重要的地形營力，釐清地震和其崩塌分布的關係有助於瞭解造山帶的地形演育和評估地震災害潛勢與風險，然而，過往地震研究經常受限於山區地震測站數量較少，或觀測資料時間跨度不足，若能夠過地震崩塌幫助解析大地震與震源斷層特性，將有助於古地震與其崩塌研究的進展。本研究重新分析1999年集集大地震的崩塌與地震與震源斷層特性的關係，透過地質調查及礦業管理中心的崩塌目錄，配合邏輯迴歸分析建立各區的崩塌方向性，並建立山崩方向性逆推演算法，用以偵測地震和震源斷層位置。研究結果顯示，崩塌方向性與地震滑移和斷層位置的關係相當密切，而非震央位置，而逆推演算法可以找出地震主要滑移區域。本研究成果地震誘發的山崩分布偵測辨識震源斷層的分析模式，將可以提供地震學在解析地震參數的額外資訊，且可應用於古地震重建之研究。

關鍵詞 Keywords：地震誘發山崩、崩塌方向性、震源斷層、地形學

摘要 Abstract：

Surface deformation assessment is a crucial aspect in understanding fault activity and mitigating disasters associated with earthquakes. Currently, near-fault deformation is primarily evaluated through in situ measurements, while regional coseismic surface displacement is estimated using geodetic tools to capture the overall deformation pattern.

However, fault activity can induce inelastic deformation tens of kilometers away from the fault line, which is known as off-fault deformation. Detecting such surface changes through in situ measurements becomes challenging. The quantification of off-fault deformation and understanding its characteristics have gained significant attention in recent years due to their potential impact on earthquake hazard assessment and mitigation. This increased focus is attributed to advancements in measurement technology.

The Hualien earthquake, which occurred in eastern Taiwan in 2018 with a moment magnitude of 6.4, was one of the most significant catastrophic earthquakes in the country in recent times. Previous studies indicate that the surface rupture was more concentrated in the northern part of the Milun fault, while the southern part exhibited scattered multiple ruptures upon entering the urban area. GNSS (Global Navigation Satellite System), Synthetic Aperture Radar (SAR), and optical satellite images were utilized to analyze the surface displacement of the region. The observations indicated a decreasing trend in surface displacement from north to south, suggesting that the Milun fault exhibited distinct lateral changes in off-fault deformation. However, due to the limitation of in situ investigations to surface rupture and satellite observations providing far-field observations without precise near-field data, there was no quantitative estimation of the lateral change in off-fault deformation. Therefore, this study employed the structure-from-motion (SfM) technique to generate high-resolution orthophotos using pre- and post-earthquake aerial images of the 2018 Hualien earthquake.The sub-pixel correlation method was then employed to calculate near-field displacements.

Combining these results with far-field observations and surface rupture data from previous studies, the proportional and lateral changes in off-fault deformation were determined.

The results of the study indicated an average north-south displacement difference of 1.56 m and an average east-west displacement difference of 1.10 m along the Milun fault. The fault line was accurately mapped based on the position of displacement drop, slightly eastward compared to previous studies. The displacement field demonstrated a clear leftward rupture along the fault, with concentrated surface rupture and narrower deformation observed in the middle part of the fault. In contrast, the southern part exhibited a wider (109m) and more dispersed surface deformation zone. Additionally, the study calculated the along-strike variation of off-fault deformation and revealed that the percentage of off-fault deformation was relatively low in the northern section (approximately 48%), but increased progressively southward (reaching approximately 81%).

關鍵詞 Keywords：off-fault deformation, 2018 Hualien earthquake, near-field rupture zone, Structure from Motion, InSAR

摘要 Abstract：

恆春半島風吹沙的海岸沙丘地形是墾丁國家公園著名的自然地景，過去雖有研究分別針對其崖頂沙丘 (翁翊家，2015；Ho et al., 2017) 與攀爬沙丘 (吳梅蘭，2021) 進行研究，但整體性的地形演育論述仍有不足。本研究使用透地雷達調查攀爬沙丘與崖頂沙丘的內部結構，與現地沉積層剖面進行比對，並與沙丘沉積層粒徑分析結果與絕對定年資料 (包括碳十四定年及光螢光定年 (OSL)資料) 進行統整，藉此重建海灘-攀爬沙丘-崖頂沙丘地景的演育過程。結果顯示：

1. 螢光定年結果顯示形成於晚全新世的攀爬沙丘與崖頂沙丘，歷經了三次主要的沙丘堆積期，攀爬沙丘沉積層中的膠結硬層以及崖頂沙丘沉積層中的古土壤層，分別指示了風沙堆積停止後的沙丘古地形面，而膠結硬層的坡度可能反映了風沙堆積時的風力強弱。

2. 攀爬沙丘與崖頂沙丘風積物的粒徑變化並非全然一致，顯示風成作用在沿著海崖地形爬升通過邊緣的過程中，在風力上產生極為顯著的變化，與現地風場測量結果 (墾丁國家公園管理處，1996；Dłużewski et al, 2023) 一致。

3. 攀爬沙丘與崖頂沙丘的蝸牛殼碳十四年代資料常出現違反疊置率的倒轉現象，顯示沙丘發育的過程中出現不同規模大小的沉積物翻轉現象 (即老沙被翻出，堆疊在新沙之上)，造成年代對比上的困難。

關鍵詞 Keywords：攀爬沙丘、崖頂沙丘、透地雷達、光螢光定年

摘要 Abstract：

海岸沙丘是海岸動態環境中重要的一環，在面對氣候變遷導致海水面變化所造成的海岸環境衝擊之下，認識海岸動態環境與其長期變動，對於人類社會的永續發展來說有重要的意義。

過去的研究顯示，東亞的海岸沙丘幾乎都是發育在全新世的海退期，距今約700至800年前的小冰期也有另一波堆積期。如韓國西南海岸沙丘是在距今8000年前至5000年前形成；日本鳥取沙丘的定年結果顯示全新世風沙堆積曾經中斷，到15世紀後才繼續堆積，且直到17世紀都仍持續往內陸增生。臺灣也有多處海岸沙丘，但針對沙丘的研究多集中在臺灣東側，如台灣東北部的福隆沙丘是形成於距今3000年前至700年前；臺灣東南部的恆春風吹沙攀爬沙丘則發育在距今4,000 前至400 年前。但上述沙丘的形成位置都位於地形變化較大，海岸腹地較小的地方，較無法看出海岸沙丘在全新世海退期的遷徙。

臺灣西南部的台南平原地形變化小且腹地廣大，除了許多現生的海岸沙丘之外，前人也在台南內陸地區觀察到許多古沙丘殘跡，如曾文溪沿岸沙丘群、台南沙丘以及沙崙沙丘。但這些古沙丘是在何時形成、如何形成以及組成物為何都尚無研究進行討論。

本研究預計使用透地雷達、粒徑分析、岩象分析以及光螢光定年針對上述台南三個丘區進行調查研究，重建臺灣西南沿海的古海岸演育過程，將台南平原古沙丘與東亞其他地區的海岸沙丘演育模式進行比較，進而探討氣候變遷可能對台灣海岸環境造成的衝擊。

關鍵詞 Keywords：關鍵詞：氣候變遷、海岸沙丘、OSL定年

摘要 Abstract：

Orogenic belts are among the most tectonically active regions globally,contributing to their significance in geological studies. The deformation front in orogenic belt areas serves as a delineating boundary between active and undeformed orogenic movements. Given the geodynamic activity and associated risks in orogenic belt regions, numerous studies concentrate on the deformation front of orogenic belts, aiming not only to understand active structures but also to predict future seismic hazards.

There is a critical need for a profound understanding and ongoing monitoring of these deformation fronts in this geographical context.

The orogenic belt of Taiwan, located at the convergence of the Eurasian Plate and the Philippine Sea Plate, is one of the most active orogenic belts in the world. It is significantly influenced by the convergence of the Ryukyu subduction zone and the Manila subduction zone. In the central orogenic belt of Taiwan, the frontal structure is the Changhua Fault. Due to the risks that may arise from deformation fronts,the goal of this study is to integrate geodetic data, such as GPS, leveling measurements, and synthetic aperture radar (SAR) data, to understand the velocity field in central Taiwan. These datasets are combined with numerical models to provide insights into the interseismic velocity field and fault-slip rates and to confirm the geometry of faults in the region.

Numerical models include two-dimensional dislocation model and three-dimensional model, which aimed to provide comprehensive understanding of the seismic hazard for the deformation front along the central Taiwan orogen.

關鍵詞 Keywords：Changhua Fault, Deformation front, Numeric model, interseismic deformation