Seismic control of large prehistoric rockslides in the Eastern Alps

Large prehistoric rockslides tend to occur within spatio-temporal clusters suggesting a common trigger such as earthquake shaking or enhanced wet periods. Yet, trigger assessment remains equivocal due to the lack of conclusive observational evidence. Here, we use high-resolution lacustrine paleoseismology to evaluate the relation between past seismicity and a spatio-temporal cluster of large prehistoric rockslides in the Eastern Alps. Temporal and spatial coincidence of paleoseismic evidence with multiple rockslides at similar to 4.1 and similar to 3.0 ka BP reveals that severe earthquakes (local magnitude M-L 5.5-6.5; epicentral intensity I-o VIII1/4-X3/4) have triggered these rockslides. A series of preceding severe earthquakes is likely to have progressively weakened these rock slopes towards critical state. These findings elucidate the role of seismicity in preparing and triggering large prehistoric rockslides in the European Alps, where rockslides and earthquakes typically occur in clusters. Such integration of multiple datasets in other formerly glaciated regions with low to moderate seismicity will improve our understanding of catastrophic rockslide drivers.

Automated summary

The study suggests that severe earthquakes triggered large prehistoric rockslides in the Eastern Alps, with preceding seismic activity potentially weakening the rock slopes leading up to the events. This highlights the role of seismicity in preparing and triggering catastrophic rockslides in the region, shedding light on the relationship between earthquakes and large rockslides in clustered environments.