Tree rings reveal the correlation between the Kaindy Lake submerged forest and the historical 1889 M 8.2 Chilik earthquake (Kazakhstan)
Résumé
Paleoseismic studies are essential to improve earthquake hazard mitigation, a challenging task in the Tian Shan mountains characterized by numerous active faults, frequent strong earthquakes, and abundant triggered landslides. Here, we date the debated formation of Kaindy Lake, the famous landslide-dammed lake in southeastern Kazakhstan, included in the UNESCO World Network of Biosphere Reserves. Our dendrochronological study compares ring-width patterns from dead trees (Picea schrenkiana) still standing in the lake with living trees growing on surrounding slopes and other trees on the landslide debris. Our results place the formation of the lake to just after 1888 A.D. (the last ring of sunken trees) and before 1898 A.D. (the first established trees on the landslide), a period for which only the 1889 A.D. Chilik earthquake (M 8.2) has been reported and caused extensive damages in the region (surface ruptures, landslides). Thus, we propose that the landslide was triggered during this historical earthquake, questioning the previously preferred date of 1911 A.D., and the local common belief. Furthermore, our results indirectly complement previous paleoseismic studies at 8.5 km away, for which the most recent event in the region was poorly defined by geochronological dating, but suggested a surface rupture associated with the 1889 A.D. earthquake. The proximity of the landslide to the surface rupture would place it in the epicentral zone of the Chilik earthquake.