High-Resolution Near-Surface Velocity Model for Depth Imaging of Mineral Deposits in the Ludvika Mining Area, Sweden

Within the H2020-funded Smart Exploration project existing legacy seismic data acquired in the Ludvika Mines are analysed in order to delineate the deposits in depth. Here we present a velocity model derived using first-break traveltime tomography, which represent the near-surface materials at high resolution and can be directly used for refraction static calculations or incorporation and for depth imaging algorithm. Our results are consistent with derived velocities from downhole logging data and show a strong vertical velocity gradient in the upper first hundred meters. In mineral exploration clear images of the subsurface and an improved characterization of mineral deposits are required to reduce the risk before drilling. Especially in prestack depth imaging workflows, which are successfully applied to hardrock seismic data, a reliable velocity model is required that represents the lateral and vertical variations in lithology and assures the robustness of the velocity model within the application of depth migration routines at the same time. A special focus of this work lies on the derivation of a detailed near-surface velocity model, which accounts for strong scattering effects due to lateral inhomogeneities as well as for topographic effects on the reflections.