臺灣造山帶西部前緣在震間期的變形與應變累積

Abstract

造山帶是地球上地質活動最劇烈和危險的區域之一，其特點是劇烈的構造活動和褶皺逆衝。造山帶的變形前緣作為一個標誌，指示了活動構造運動和非活動構造運動之間的邊界。一般來說，變形前緣也是造山帶最活躍的構造區域，因此迫切需要對該區域進行深入了解和持續監測。 臺灣的造山帶是世界上最活躍的造山帶之一。在臺灣中部，造山帶的前緣構造是彰化斷層。據信彰化斷層最近一次引發的地震發生在1848年，距今已近180年。車籠埔地震的發生使得彰化斷層及臺灣中部造山帶的變形前緣更值得進一步調查。因此，本研究集中於彰化斷層的應變積累和地震潛勢。研究目標是整合各種大地測量數據，包括GNSS、水準測量和InSAR，分析地表速度，並利用地表速度的數據建立模型，以確定斷層的滑移虧損速率。 本研究發現，儘管造山活動向西推進，且彰化斷層處於最前緣，但彰化斷層並未顯示出最高的滑移虧損速率，反而是車籠埔斷層顯示出最高的滑移虧損速率。然而，車籠埔斷層剛剛進入新的地震週期，而彰化斷層已在其當前週期中持續了近180年。一旦彰化斷層引發地震，將對超過300萬人構成重大風險。因此，不能忽視彰化斷層相關的潛在危害。

The orogenic belt is one of the most geologically dynamic and hazardous areas on Earth, characterized by intense tectonic activity and fold-and-thrust belts. The deformation front of the orogenic belts serves as a marker, indicating the boundary between active and inactive tectonic movements. Generally, the deformation front is also the most active structure of orogenic belts, and there is an urgent need for a thorough understanding and continuous monitoring of this region. The orogenic belt in Taiwan, which is one of the most active orogenic belts in the world. In the central Taiwan, the frontal structure of the orogenic belt is the Changhua fault. The most recent earthquake triggered by the Changhua fault is believed in 1848, nearly 180 years ago. The out-of-sequence Chi-Chi earthquake makes the Changhua fault and the deformation front of the Taiwan central orogenic belt even more worthy of investigation. Therefore, this study focuses on the fault strain accumulation and seismic potential of the Changhua fault. This research aims to integrate varied geodetic data including GNSS, leveling, and InSAR to analyze surface velocities, and conducting a model with geodetic data to determine the slip deficit rates. It is found that despite the westward propagation of orogenic activity and the Changhua fault being at the forefront, the Changhua fault does not show the highest slip deficit rate. Instead, the Chelungpu fault shows the highest slip deficit rate. However, the Chelungpu fault has just started a new seismic cycle, whereas the Changhua fault has been in its current cycle for 176 years, posing a significant risk to over 3,000,000 people in the event of an earthquake triggered by the Changhua fault. Therefore, the potential hazards associated with the Changhua fault should not be ignored.