九二一集集大地震後的觀測顯示，位於車籠埔斷層兩端的鯉魚潭與曾文磁力站皆錄得明顯的震前磁場異常，並與地震發生時間高度吻合。此類震前磁力變化被認為可能反映孕震區岩層在應力累積與裂隙生成過程中所引發的局部電磁效應，因而使地磁資料成為探討地震前兆的重要指標。中央氣象署自 2018 年起全面更新三分量磁力儀，為地磁微脈動與地震關聯性研究提供寶貴資料。本計畫旨在全面檢視三分量地磁觀測站的資料品質，並運用多項分析方法—包含日變化振幅比值法、能量譜密度分析，以及主成分分析—以識別潛在局部異常並探討其與地震活動之可能關聯。透過系統化的資料評估、跨測站比對與降維分析，期望釐清地震前磁場異常的特性與來源，並建立地磁背景模型。 ;Following the observations made after the 1999 Chi-Chi earthquake, the Liyutan and Tsengwen magnetic stations—located near the northern and southern ends of the Chelungpu Fault—recorded clear preseismic magnetic anomalies that closely coincided with the earthquake occurrence. Such magnetic variations are thought to reflect localized electromagnetic effects associated with stress accumulation and microfracture development within the seismogenic zone, making geomagnetic observations an important indicator for studying potential earthquake precursors. Since 2018, the Central Weather Administration has fully upgraded its instrumentation to tri-axial magnetometers, providing high-quality data for investigating geomagnetic micropulsations and their connection to seismic activity. This project aims to comprehensively evaluate the data quality of Taiwan’s tri-axial geomagnetic stations and apply multiple analytical approaches—including daily variation amplitude ratio analysis, power spectral density analysis, and principal component analysis (PCA)—to identify potential local anomalies and examine their possible relationship with earthquakes. Through systematic data assessment, cross-station comparison, and dimensionality reduction techniques, the project seeks to clarify the characteristics and origins of preseismic magnetic anomalies and to establish a robust geomagnetic background model.
