Cascading rupture of large strike-slip fault bends: Evidence from paleoearthquakes in the Xianshuihe fault zone, Eastern Tibetan Plateau

The restraining and releasing bend region, encompassing the South Qianning, Kangding, and North Moxi segments, occupies a distinctive position within the Xianshuihe fault zone and plays a pivotal role in the analysis of seismic hazards. Our study focused on paleoearthquake research on the Qianning segment of the Xianshuihe fault zone through the integration of tectonic geomorphology, trench excavations, and radiocarbon dating methodologies. Three events, designated as ET1-ET3, have been found, occurring at 635-519, 823-672, and 3515-1482 yr B.P., respectively. A chronological framework for earthquake events has been established since the Holocene. The coefficient of variation (CoV) (0.75 reveals a weakly periodic recurrence model governing the activity of the Qianning segment. Moreover, both the Qianning and Kangding segments exhibit heightened susceptibility to cascading ruptures within the context of a single earthquake. The integration of shallow and deep data reveals a noteworthy transformation in the fault structure, transitioning from a solitary deep structure within the Qianning segment to a flower structure in the Kangding segment. This structural evolution is attributed to the migration of activity from the Yalahe Fault to the Selaha Fault and Zheduotang Fault, resulting in the short-cutting process within the Xianshuihe Fault Zone.