Preliminary application of optically stimulated luminescence (OSL) dating on fault gouge from the Yangsan Fault Zone, Korean Peninsula

초록

This research examines the feasibility of applying optically stimulated luminescence (OSL) dating of fault gouge to constrain the timing of surface-rupturing events in the Yangsan Fault Zone on the Korean Peninsula. The timing of Quaternary faulting has traditionally been inferred indirectly through dating faulted and unfaulted sediments, underscoring the need for a more direct approach. To assess whether OSL ages of fault gouge can yield reliable age constraints, fault gouge and sediment samples associated with surface ruptures were dated from three trench exposures. At two locations with comparable stratigraphic relationships, the surface ruptures cut the lower units and are unconformably overlain by the upper units. The OSL ages of the fault gouge bands fall between the ages of the faulted and unfaulted units, providing maximum age constraints for the most recent earthquakes (MREs). At the third location, although the surface rupture cuts all units, the OSL age of the gouge patch is indistinguishable from the depositional ages of the surrounding sediments, likely reflecting mixing between sediments and gouge injected during Quaternary faulting. Whether these OSL ages record the MRE remains uncertain. Nevertheless, they provide conservative maximum age constraints, indicating that the surface-rupturing events occurred after these ages. Overall, these findings highlight both the potential and the limitations of using OSL dating of fault gouge to constrain Quaternary fault activity. Continued research is required to refine dating methods and obtain additional high-resolution chronological data to more robustly constrain the timing of the MRE and improve future seismic hazard assessments.

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