Evidence for Large Holocene Earthquakes Along the Yangsan Fault in SE Korea

Recent research published in the GSA Bulletin (https://pubs.geoscienceworld.org/gsa/gsabulletin/article/doi/10.1130/B37275.1/645931/Evidence-for-large-Holocene-earthquakes-along-the?searchresult=1) reveals significant paleoseismic evidence for large earthquakes along the Yangsan fault in the southeastern Korean Peninsula. This fault, a prominent NNE-SSW striking active right-lateral strike-slip fault, spans approximately 200 km and has the potential to generate significant seismic events. The study involved detailed three-dimensional trench excavations across the central segment of the fault, uncovering evidence for at least five surface-rupturing earthquakes preserved in Quaternary fluvial deposits.

The most recent seismic event occurred around the third century CE, with lateral displacements ranging between 4.5 and 5.3 meters (Figure 1; modified from Naik et al., 2024), suggesting the occurrence of large magnitude earthquakes (around Mw 7) along this fault. This study is crucial as it provides the first direct evidence of such significant earthquakes in this region, helping to refine seismic hazard assessments for the Korean Peninsula. The research underscores the importance of continuous monitoring and detailed geological investigations to understand the long-term behavior of active faults and to mitigate earthquake hazards effectively.

Figure 1: Illustration of observed channel offset along the Yangsan Fault (taken from https://pubs.geoscienceworld.org/gsa/gsabulletin/article/doi/10.1130/B37275.1/645931/Evidence-for-large-Holocene-earthquakes-along-the?searchresult=1).