The tectonic activity of the Central Range Fault in Taiwan: insights from patterns of erosion rate and geomorphic evidence in the eastern Central Range

The rapid collision between the continental margin of the Eurasia Plate and the Luzon Arc on the Philippine Sea Plate has built the island of Taiwan. The suture zone of the arc-continental collision that divides the Coastal Range to the east and the Central Range to the west is called the Longitudinal Valley. The Central Range and the Longitudinal Valley are bound by the Central Range Fault, which has long been proposed as an active fault. Still, limited field evidence of its activity has prevented us from comprehensively understanding its fault trace, geometry, and faulting mechanism. Surface ruptures caused by the 2022 Taitung Earthquakes revealed that the Yuli Fault, which also ruptured in the 1951 earthquakes, is a west-dipping fault and belongs to the Central Range Fault. This event thus brought the Central Range Fault back into the spotlight. In this work, we looked for potential geomorphic signatures associated with the fault activity using geomorphic indicators such as channel steepness, channel width, and grain size distribution of sediments in the main drainage basins along the middle part of the eastern Central Range. The channel width was determined by mapping the channel borders using SPOT images captured in 2003 and 2022 to determine the potential variance induced by recent mass-wasting events. In addition, we collected detrital sediment samples from these basins to derive basin-wide erosion rates based on in-situ 10Be concentrations. We combined all these results to discuss the evolution of the landscape in response to the activities of the Central Range Fault.