Tree-ring correlations suggest links between moderate earthquakes and distant rockfalls in the Patagonian Cordillera

Abstract

Earthquakes with magnitudes M > 7 can trigger large landslides and rockfalls at epicenter distances of up to 400 km, whereas moderate shaking ( M = 5–7) is generally thought to result in abundant co-seismic mass movements in the vicinity of the epicenter. Although one might anticipate that large magnitude earthquakes off the Chilean coast would result in abundant rockfall in the Patagonian Cordillera, only limited research has explored this hypothesis. Here, we use tree-ring records from 63 cross-sections of century-old (103.9 ± 40.1 yr) Nothofagus pumilio trees to develop a calendar-dated record of small rockfall events (10 1 –10 2 m 3 ) on a talus slope located next to Monte Fitz Roy (El Chaltén, Argentina; 49°4′S, 72°57′W). The resulting rockfall record is 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 (up to 300 km away) and with moderate intensity ( M = 5–7). About one third of the rockfalls are triggered by factors other than earthquakes, predominantly in spring when freeze-thaw cycles occur frequently at the site. Despite the fact that seismicity is not the only trigger of rockfall activity at Cerro Crestón, at the foot of Monte Vespignani, we conclude that, in regions where topographic amplification plays a role, small rockfalls can be triggered by earthquakes of moderate intensity at large distances from the epicenter.

The Use of UAV-Acquired Multiband Images for Detecting Rockfall-Induced Injuries at Tree Crown Level

“…Mainieri et al [84] reported that abrupt growth suppression was the least common response of rockfall growth injuries. Stoffel et al [85] concluded that after rockfall injuries, 13% of the studied coniferous trees experienced strong growth after the injuries and that suppressed growth due to reduced vitality or photosynthesis was rare (only in 4% of cases). Since trees can react differently after wounding and considering that no branches or tree tops were affected at the Jelovica site, we presume that this is the reason why no differences between the injured and uninjured trees were present as yet.…”

Forest Resilience in the Himalayas Inferred From Tree Growth After Earthquake Disturbances

“…On the other hand, such events might facilitate the growth of trees by reducing neighborhood competition (Kitzberger et al., 1995), supplying sufficient soil nutrients and moisture (Bekker et al., 2018; Cheng et al., 2012) or enhancing photosynthesis (Mohr et al., 2021). Hence, variations in annual growth in trees (tree‐ring width data) are often used to date earthquake events and thus, are considered as one of the potential proxies in understanding earthquakes' impacts on forests (Pedrera et al., 2014; Stoffel et al., 2019).…”

Holistic rockfall risk assessment in high mountain areas affected by seismic activity: Application to the Uspallata valley, Central Andes, Chile

“…The Andean mountains, the longest mountain chain of the world and the second highest, is periodically affected by large magnitude earthquakes. Resulting ground motions can trigger several adverse events such as landslides and floods, and are considered as one of the main drivers of local rockfall activity (Stoffel et al., 2019). Losses directly related to earthquake hazard (e.g., collapse of buildings and failure of infrastructures) are increasingly well understood and quantified.…”