Analysis of seismic noise sources in an open pit mining environment.

We present the characterization of the seismic ambient noise wavefield in the open-pit Riotinto mine (southern Spain), in the mainframe of a collaborative research project aiming to use the ambient noise wave field to monitor structural subsurface changes in near real-time. Noise characterization is based on a dense seismic network of 30 stations located along a 1-km long segment of a tailings dam. We first describe the most frequent transient signals detected, including local and distant earthquakes, blasting, and vehicles. The time variations in the amplitude of the 10-40 Hz frequency band are then used to define three phases of activity during the recording period. The highest amplitudes are directly related to the regrowth of the dam wall carried out to properly store the constantly increasing amount of tailings. In the third phase, the seismic noise is dominated by the deposition of tailings into the deposit, allowing the use of seismic data to monitor in detail the evolution of the deposition process. The detailed knowledge of the sources of noise in the Riotinto mine provides the basis for developing ambient noise seismic interferometry methods to monitor the physical properties of the subsurface of this and other open-pit mining areas. This research is part of the R+D+I project CPP2021 009072 funded by MCIN/AEI/10.13039/501100011033 (Ministry of Science, Innovation and Universities/State Innovation Agency) with funds from the European Union Next Generation/PRTR (Recovery, Transformation, and Resilience Plan).