Earthquakes trigger rockfalls at very large epicenter distances in Patagonia

Earthquakes can trigger large landslides and rockfalls at epicenter distances of several hundreds of kilometers. In a study recently published in Nature Scientific Reports, Markus Stoffel and co-authors used tree-ring series of Nothofagus trees to develop a calendar-dated record of rockfall events on a talus slope located next to Monte Fitz Roy (El Chaltén, Argentina). The resulting rockfall record was then used to infer that subduction zone seismicity at the Triple Junction and intraplate shaking around Lago Argentino almost systematically caused rockfall activity at this site, even if seismicity occurred at large distances (<300 km away) and with moderate intensity (M = 5–7). The authors conclude that, in regions where topographic amplification plays a role, small rockfalls can be triggered by earthquakes at significantly larger distances from the epicenter than previously thought.