Combined fibre-optic sensing and nodal recorders for active-source seismic characterization of mine tailings

Abstract

Abstract As the mining industry shifts toward more responsible and lower-impact practices, mine tailings are increasingly regarded as a secondary resource that can be sourced into the raw-material supply chain. However, limited knowledge of subsurface geometry at many historical tailings sites leads to uncertainties in volume and resource estimates. High-resolution seismic imaging can provide improved characterization of such sites. Here, we present the results of a seismic survey conducted in 2024 on tailings at Blötberget in central Sweden. The data were acquired using a combined, partly collocated setup consisting of a sparse 3D nodal array, a landstreamer and distributed acoustic sensing (DAS) systems. The objective was to characterize the tailings and to optimize the acquisition and processing strategies for our application. Through 2D reflection seismic imaging, layer-based refraction travel-time modelling and travel-time tomography, we obtain well-constrained P-wave velocities for the tailings on the order of 300–350 m/s. Additional 3D travel-time modelling yielded volumetric estimates, from which we estimate a total tailings tonnage of approximately 4 Mt. Finally, we demonstrate that surface DAS can serve as a complementary recording system, capable of delineating the tailings when fibre cable-ground coupling conditions are favourable. The survey serves as a pilot for future mine tailings investigations and related near-surface characterization efforts, and we highlight the benefits of using multi-element seismic recording arrays for such purposes.