Tree-ring analysis in the reconstruction of slope instabilities associated with earthquakes and precipitation (the Crimean Mountains, Ukraine)

Abstract

The Crimean Mountains in Ukraine constitute a seismically active region that is abundant in various types of mass movement. The limestone escarpments that rise above the Black Sea coast in the vicinity of the town of Yalta are particularly subject to considerable rockfall, landslide and debris flow processes that often endanger infrastructure and human life. One of these very active slopes is the area of the ancient Taraktash rockslide, characterised by active block-type movements (lateral spreading, toppling, and incipient sliding), rockfalls, ongoing sliding activities and debris flows. The aims of this study were (i) to employ tree-ring analysis to reconstruct a record of slope instabilities (mainly block-type movements, rockfalls, landslides and debris flows) within the Taraktash slope deformation over a period of more than two centuries and (ii) to establish the degree of correlation between periods of enhanced slope activity and both historical earthquakes and climatic data. The temporal frequency of significant slope processes was addressed through a tree-ring analysis that took 738 increment cores from 255 Crimean pine trees Pinus nigra ssp. pallasiana. The tree-ring record reveals periods of increased activity of block-type movements, rockfalls and landslides during the major earthquakes in 1790, 1875, 1927 and 1986. Although the slope processes studied are predominantly driven by seismic activity, their intensity and duration are also dependent on climatic factors. This is especially true for landslides and debris flows, which occurred mainly in years characterised by high precipitation totals.