Taiwan's Central Geological Survey has identified 33 major earthquake fault lines. The most active include the Sanyi, Hsinchu, Chaochou, and Chiayi faults. These fault zones regularly trigger earthquakes posing major risks to surrounding areas.
The 1999 Chi-Chi earthquake resulted from displacement along the Chelungpu and Pakuashan fault zones. This fault system extends approximately 100 kilometers from Taichung through Nantou and is one of Taiwan's most active fault systems. The earthquake was followed by numerous magnitude 5+ aftershocks.
The Sanyi Fault lies between Hsinchu and Taichung, classified as high-risk. The Chiayi Fault extends from Pingtung into the Taiwan Strait. The Hsinchu Fault experienced significant surface rupture during the 1999 earthquake.
Eastern regions including Hualien and Taitung have multiple active faults: the Anzhang, Ikeda, and Guilai faults. Their activity results in high earthquake frequency in eastern Taiwan. The Geological Survey regularly monitors these faults and assesses future earthquake potential.