Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

252 PATA Days 2024 Through these various investigative processes, two trenching studies were conducted to confirm paleo surface ruptures. Also, six pits were excavated for dating purposes to determine the ages at each geomorphic surfaces. Samples collected from each site are currently being analyzed using three different dating methods: (1) cosmogenic nuclide dating (10Be depth profile), (2) optically stimulated luminescence (OSL), and (3) radiocarbon dating. R E S U LT S The study area is characterized by an alluvial fan originating from the eastern mountains, intersected by from east-to-west flowing minor channels and the Gigye Stream flowing from north to south at the toe of the alluvial fan (Fig. 1a). The southern boundary of the alluvial fan features small streams flowing from east to west, developing terrace surfaces from T0 to T4 (Fig. 1b). T0 represents the current river level at an elevation of about 23 m, while T1 is at approximately 25-28 m. T2 is at 32.5 m, T3 at 37 m, and T4 at about 43 m. These geomorphic surfaces are displaced dextrally due to NNE-SSW oriented linear structures (Fig. 1b). The T1‒T2 riser is about 20 m, and the T2‒T3 riser has a dextral offset of about 29 m. To the north along this lineament, fluvial terrace forms are observed, also showing dextral displacement (Fig. 1c). Fig. 1: LiDAR hillshade map (0.5 m/pixel) showcasing the development of an alluvial fan in the study area. (a) The alluvial fan originates from the eastern mountains, with fluvial terraces formed by east-to-west flowing streams. (b) Distribution of four geomorphic surfaces on the southern side of the alluvial fan, where dextral offsets induced by the YF are observed. (c) To the north of the alluvial fan, terrace risers developed by the streams are offset dextrally (trench location shown in Fig. 3b).