Modeling Seismic Hazard and Landslide Potentials in Northwestern Yunnan, China: Exploring Complex Fault Systems with multi-segment rupturing in a Block Rotational Tectonic Zone

The Northwestern Yunnan Region (NWYR), located on the southeastern edge of the Tibetan Plateau, is characterized by a combination of low-crustal flow and gravitational collapse, giving rise to a complex network of active faults. This presents significant seismic hazards, particularly due to the potential for multi-segment ruptures and resulting landslides, as demonstrated by the historical 1515 M7.8 Yongshen Earthquake. This article presented a novel seismic hazard modeling study for the NWYR, integrating fault slip parameters and assessing multi-segment rupturing risks. Among the four potential multi-segment rupture combination models examined, Model 1, characterized by multi-segment rupture combinations on single faults, particularly fracturing the Zhongdian fault, emerges as the most suitable for the NWYR, supported by the alignment of modeled seismicity rates with fault slip rates. Our analysis demonstrated that peak ground-motion acceleration values, calculated with a 475-year return period from modeled seismicity rates, exhibited a strong correlation with fault distribution, averagely higher than the China Seismic Ground Motion Parameters Zonation Map. Furthermore, we conducted simulations to forecast landslide occurrence probabilities across our peak ground-motion acceleration distribution map. Our findings underscored that the observed combinations of multi-segment ruptures and their associated behaviors were in alignment with the small block rotation triggered by the gravitational collapse of the Tibetan Plateau. This result highlighted the intricate interplay between multi-segment rupturing hazards and regional geological dynamics.