Comprehensive geometric characterization of the subsurface using Microseismic Resonance: identifying sinkholes by modelling the bedrock surface and karstic features in a challenging environment

Abstract

This study presents a comprehensive assessment of the subsurface characteristics at a Unigel processing facility in Pedra Blanca, Sergipe, Brazil, utilizing Microseismic Resonance (MSR). The facility experienced the emergence of sinkholes and depressional features near critical infrastructure, prompting the need for a thorough subsurface characterization. MSR, a burgeoning microseismic technique, was employed due to its ability to geometrically characterize subsurface structures without the limitations of large geophone arrays. Fieldwork involved MSR data collection on a 10m by 10m grid over a 37.14 hectare area, complemented by borehole data and a gravity survey. Results revealed the intricacies of complex stratigraphy with Quaternary fluvial deposits overlying Early Cretaceous carbonates with karstic morphology. MSR data processing produced a holistic geometric model of the subsurface, including the identification of karstic features. Comparison with borehole data demonstrated high accuracy, with MSR Local Component (LC) data rendering a bedrock surface of approximately 99% accuracy. MSR Full Spectrum data (FS) is correlated with the gravity study validating the presence of karstic structures. This study showcases MSR as a powerful, non-invasive tool for rapid and accurate subsurface characterization, crucial for infrastructure security and environmental assessment