Present-day crustal movements in the Western Caucasus region from GNSS data and analysis of the regional geodynamic network configuration

Abstract

Relevance. The Western Caucasus is characterized by spatially heterogeneous present-day crustal motions and an active fault-block structure. Published GNSS site velocities cover different time intervals and are reported in both tabular and map form, which complicates their joint deformation analysis. The problem is especially important for the Tuapse–Sochi segment, where active structures cross a densely developed coastal and mountain area. Aim. This study compiles published horizontal velocity estimates for the Western Caucasus, evaluates the present-day strain field, and tests whether the geometry of the combined network is suitable for finite-element analysis. Methods. A data set of 54 GNSS sites was assembled from three published sources. Where numerical values were unavailable, maps were georeferenced in QGIS and the start and end of each velocity vector were digitized; vector magnitude, azimuth, and east and north components were then derived using the source scale. Principal strain rates, dilatation, and total shear strain rate were calculated. The network was triangulated using the Delaunay algorithm, and element geometry was assessed by the circumradius-to-inradius ratio R/r. Results. The regional field confirms coherent north-northeastward motion, while local domains of contraction, extension, and shear localization occur within the study area. The Tuapse–Sochi strain field is asymmetric and mosaic-like, with major contrasts spatially associated with fault boundaries and fault-intersection zones. Most triangles have optimal or acceptable geometry, whereas unfavorable elements occur mainly along the network margins. Conclusions. Combining heterogeneous published velocities reveals robust regional patterns, but the amplitudes of local anomalies must be interpreted with regard to reference-frame differences, observation-span variability, and graphical digitization uncertainty. The proposed R/r classes provide explicit element-selection rules and support further development of continuous GNSS monitoring in the Greater Sochi area.