Latest quaternary active faulting and paleoearthquakes on the Yalahe Fault of the Xianshuihe Fault Zone, Eastern Tibetan Plateau

The Yalahe Fault (YLHF) is a sub-strand of the Xianshuihe Fault Zone (XSHF) that plays an important role in understanding the structural deformation pattern of the Kangding segment and analyzing the seismic hazards in this area. However, little is known regarding the recurrence patterns and characteristics of large earthquakes along the YLHF. We reveal six recent paleoearthquake events on the YLHF using tectonic geomorphology, trench excavations, and radiocarbon dating. The six events, E6-E1, are constrained to have occurred during (from oldest to youngest, respectively) 20,975-20,749, 18,981-18,817, 10,437-10,252, 7168-6269, 3465-2490 yr BP, and after 1380 +/- 60 CE. The most recent event may correspond to the 1700 CE similar to M 7 earthquake. The average recurrence interval was 3365 yr in the Holocene, and the coefficient of variation was 0.13, indicating that the YLHF follows a quasiperiodic recurrence model. The YLHF may experience cascading ruptures with two adjacent faults (Selaha and Zheduotang). The range of activity was located north of Huiyuan Temple and south of Jingai. Deformed strata show that the YLHF is kinematically characterized by transtension. In addition, the YLHF accumulated parts of the slip rate of the single-stranded XSHF. Therefore, the YLHF plays a significant role in the tectonic deformation of the XSHF in the Kangding segment with a high seismic hazard.