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Seismic control of large prehistoric rockslides in the Eastern Alps

P. Oswald, M. Strasser, C. Hammerl, J. Moernaut

Nature Communications, 2021

67 citations

Abstract

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 ~4.1 and ~3.0 ka BP reveals that severe earthquakes (local magnitude ML 5.5–6.5; epicentral intensity I0 VIII¼–X¾) 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. The authors here present a multi-lake paleoseismological approach to evaluate the role of earthquakes in causing a spatio-temporal cluster of large, prehistoric rockslides between 3000 and 4200 years ago in the Eastern European Alps and for which the triggering mechanisms are still debated.

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