Reliable estimates of the geological slip rate for slowly deforming intraplate strike-slip faults are limited, as cumulative offsets are usually small and surface ruptures are often distributed across multiple strands. Here, we constrain a minimum late Quaternary slip rate along a segment of the Yangsan Fault (YSF), southeastern Korea, by integrating high-resolution LiDAR data, historical aerial photographs, optically stimulated luminescence (OSL) dating, terrace-riser restoration, and paleoseismic trench observations. Geomorphic analysis identified offset fluvial terraces (T1 and T2), and terrace-riser reconstruction yields dextral horizontal offsets of ~19.03 m. Swath profiles show that vertical displacement along the main fault is minor relative to the horizontal component, with subsidiary structures accommodating larger local vertical displacements. Five OSL ages from the T2 surface yield a weighted mean age of 103.14 ± 3.17 ka, and the best-preserved T2–T1 riser gives a horizontal offset of 19.03 ± 1.45 m, indicating a minimum dextral slip rate of 0.15–0.23 mm/yr. The resulting minimum slip rate overlaps a low estimate from the nearby Byeokgye section, and is lower than the long-term geomorphic rate reported from the Bangok section, suggesting that both along-strike segmentation and distributed deformation influence slip rate variability along the YSF. Our results emphasize the complexity of deformation along a slowly slipping intraplate strike-slip fault and suggest that slip rates along the YSF should be interpreted in the context of fault-zone complexity rather than as a single representative value.
Kim et al. (Mon,) studied this question.