Application of passive seismic interferometry for mapping mining waste storage facilities: A case study of Pyhäsalmi mine in Finland

Obtaining knowledge about the structural, geotechnical and hydrogeological conditions of mining waste storage facilities (e.g., tailing storage facilities, TSF) is an important task for mining waste management. From the existing applied geophysics techniques, high-resolution controlled source seismic methods are the most appropriate due to their superior spatial and depth resolution. However, the TSF areas are not often accessible for installation of seismic instruments and application of controlled source. Moreover, TSF areas in active mine sites are characterised by high-level of seismic and acoustic noise, produced by mining operations and other human activities at mine sites. In this study, we show that these problems can be addressed by utilizing passive seismic interferometry, in which cross-correlation of ambient seismic noise is used to obtain the Empirical Green's function (EGF's) of the studied medium. We used this method to evaluate seismic velocities in the TSF and in the near-surface bedrock at the site of the Pyhäsalmi underground mine in Finland. We used the ambient seismic noise recorded in two seismic experiments in the area. In the first experiment, the data were acquired in 2013 along a line 10 km long crossing the area of the underground mine. The second experiment was carried out in the TSF area in 2019. We obtained S-wave velocity models of both bedrock and the TSF by applying multichannel analysis of surface waves (MASW) to surface wave parts of Empirical Green's Functions (EGFs). The analysis of autocorrelation functions of passive seismic data recorded on the TSF surface allowed to us retrieve reflected arrivals from the boundaries inside the TSF. At the same time, we used amplitudes of surface wave parts of EGF's to obtain information about attenuation of surface waves in TSF. Our results show that passive seismic interferometry and interpretation of passive seismic data by different techniques can be a useful tool for inspection of TSF of active mines