Response of tree rings to earthquakes during the past 350 years at Jiuzhaigou in the eastern Tibet.

Abstract Trees growing in the tectonically active and climatically sensitive regions, such as the Tibetan Plateau, frequently suffer damage from strong earthquakes and extreme hydro-climatic events. Spruce trees in the Jiuzhaigou National Park exhibited abrupt periods of growth suppression with durations of 3–9 years, which was demonstrated to have recorded five seismic events during the last 350 years after excluding the climatic impacts. The ring-width reductions occurred immediately after earthquakes in the growing seasons of 1748, 1879 and 2017, and one year later in 1961 when the earthquake occurred after the growing season in 1960. In contrast, seismic signals of the 1976 earthquake were moderated in the tree-ring indices by improved climatic conditions in 1975. The intensity prediction equation and isoseismal modelling results suggested that past earthquakes required a minimum intensity threshold of 6.2–6.8 MMI to significantly impact tree growth, thus indicating a minimum magnitude threshold of Mw5.3 for near-field (≤20 km) earthquakes and Mw7.4 for regional (≤115 km) earthquakes. These results would greatly improve the dendroseismological reconstruction of past earthquake characteristics and the valid assessment of future probabilities in the eastern Tibet, and help to identify and eliminate seismic signals in the dendroclimatological studies in the hazardous environments.