Paleo-landslide analysis reveals underestimated seismic hazards in the outer Western Carpathians

Paleoseismic methods frequently prove ineffective in stable continental interiors, where the rarity of surface-rupturing earthquakes can result in a significant underestimation of long-term seismic hazard. To address this limitation, an integrated approach was developed that transformed paleolandslides into quantitative paleoseismic indicators. This method combined detailed morphometric and structural analyses with dynamic back analysis, incorporating velocity-dependent friction laws from rotary shear experiments into Newmark displacement analysis. Results were validated using discrete element runout modeling (particle flow code in three dimensions). When applied to a well-preserved paleolandslide in the Outer Western Carpathians, a region traditionally considered as low hazard, this approach revealed a critical seismic triggering threshold. The analysis indicated that a magnitude of M7.1–7.3 earthquake at a short distance (~1.2 km) was required for initiating catastrophic failure, consistent with the observed long runout and liquefaction features. The findings presented herein constitute the first physical evidence for M7+ paleoearthquakes in the region, challenging existing seismic hazard assessments for Central Europe and demonstrating that stable continental interiors can host large, although infrequent earthquakes.