Long-term evolution and type-specific rainy-season activity of post-seismic geohazards in Southwest China

Abstract. Long-term evolution of post-seismic geohazards represents a critical yet complex challenge in earthquake-affected regions. This study systematically investigates the spatiotemporal patterns of post-seismic geohazard evolution following three major seismic events: the 2008 Wenchuan earthquake (Mw7.9), 2013 Lushan earthquake (Mw6.6), and 2017 Jiuzhaigou earthquake (Mw7.0), focusing on four representative counties (Wenchuan, Beichuan, Lushan, and Jiuzhaigou County) in Southwest China. The results show that: (1) post-seismic geohazard activity showed an intermittent clustered outbreak pattern; (2) geohazards were mainly concentrated in valley-related geomorphic units, with county-level differences characterized by reactivation–expansion, spatial inheritance, localization, and contraction; (3) monthly records excluding earthquake-month records showed a clear rainy-season concentration, with 78.1 % of geohazards occurring from June to August; and (4) Beichuan and Lushan showed clearer weakening trends, whereas Wenchuan and Jiuzhaigou remained in low-level persistent activity stages and should receive continued monitoring attention. These findings provide useful insights for long-term geohazard monitoring and risk mitigation in earthquake-affected mountainous regions.