Abstract:Two trenches LT1301 and SLT1204 were excavated in the Benge-Cunge section of Litang left-lateral strike-slip active fault zone in the southeastern margin of the Qinghai-Tibet Plateau. Based on the detailed division of the paleoearthquake events revealed in the two trenches and the ages of 10 OSL and 13 14C samples obtained, the occurrence ages of paleoearthquake events in the northern part of the Litang fault zone are determined. The results show that the two trenches have revealed at least four paleoearthquakes events. Among them, the small-scale trench LT1301 only reveals one paleoearthquake, which may be a historical earthquake in 1729 A.D. or a major earthquake between 950A and 1.0 ka. The above two possibilities are still uncertain due to insufficient chronological data at key locations. The larger trench SLT1204 reveals four paleoearthquakes including the one in the trench LT1301. The earliest three paleoearthquake event I occurred before 9.9ka. Events II, III and IV occurred between 1729 and 4.8 kaBP with a recurrence interval of 1.6 ka. The paleoearthquakes in the northern part of the Litang fault zone in Western Sichuan indicate that the recurrence of large earthquakes in the fault has non-linear characteristics and does not conform to the characteristic earthquake model. The frequency of large earthquakes in the late Holocene increased significantly, indicating that the fault is in the stage of cluster activity.