Identification of the Geological Structure of the Western Polesie Wetlands Using a Multicomponent Surface Wave Analysis Approach

Abstract

The wetlands of Western Polesie form one of the most valuable peatland–lake complexes in Poland. Their functioning is strongly controlled by the geological structure of the subsurface and local hydrogeological conditions. Progressive degradation of these environments, driven in part by land drainage and changes in the water regime, poses a significant threat to the ecological integrity of the region and may, in the long term, adversely affect its hydrological and hydrogeological conditions. A reliable assessment of ongoing environmental changes therefore requires detailed characterization of the geological structure, particularly within the near-surface zone. This study evaluates the applicability of non-invasive engineering geophysical methods for investigating the shallow geological structure of Western Polesie, with particular emphasis on organic soils, including peat. Multichannel analysis of surface waves (MASW) was applied using both Rayleigh and Love waves, allowing the two wave types to be analyzed independently and their results to be compared. Four survey profiles representing contrasting lithological conditions were selected on the basis of GIS and cartographic analyses. These included the processing and interpretation of a Digital Elevation Model (DEM) and its derivatives, such as slope, aspect, and hillshade maps, together with geological and topographic data and a spatial assessment of site accessibility. Field surveys were conducted in 2025, and the acquired seismic data were processed to obtain two-dimensional shear-wave velocity (Vs) sections. The results revealed distinct differences in the sensitivity of Rayleigh and Love waves to variations in the mechanical properties of the subsurface associated with lithological changes. Integrating the results obtained from both wave types reduced interpretational ambiguity and enabled a more robust reconstruction of the near-surface geological structure. The findings demonstrate that a multicomponent MASW approach can substantially improve geological characterization in wetland environments and represents a valuable tool for investigating and supporting the protection of degraded organic soils in Western Polesie.