# Digital Processing of Seismic Data from Open-Pit Mining Blasts
## 4 Results and Discussion  
The experiment results are reflected by seismograms showing the ground flow velocity change with respect to three coordinates--radial, tangential and vertical. Three components of the ground velocity at a distance of 13 m are shown in Figure 3.  
Figure 1: The experiment layout. Figure 2: The experiment layout. The seismograms were processed in several ways, as described below. The Fourier transform provides the spectra as shown in Figure 4. Table 1 presents the dominant frequency and amplitude for every component of the signal. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Distance, m**} & \multicolumn{2}{c}{**Train**} & \multicolumn{2}{c}{**Vert**} & \multicolumn{2}{c}{**Long**} \\ \cline{2-7}  & **Dominant Frequency** & **Amplitude** & **Dominant Frequency** & **Amplitude** & **Dominant Frequency** & **Amplitude** \\ \hline
25 & 161.4 & 0.021 & 167.4 & 0.006 & 2.375 & 0.011 \\
22 & 159.2 & 0.008 & 168.5 & 0.01 & 2.3 & 0.022 \\
19 & 157.3 & 0.1 & 116.6 & 0.017 & 2.25 & 0.017 \\
16 & 157.4 & 0.018 & 107.9 & 0.033 & 2.125 & 0.031 \\
13 & 147.8 & 0.03 & 85.5 & 0.077 & 2 & 0.058 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Dominant frequency and amplitude dependency on the distance for each component of the signal. Figure 4: The 13 m Long signal frequency spectrum. Figure 3: Three components of ground velocity at 13 m.  
From Table 1, it is seen that at low frequencies (up to 30 Hz) the dominant frequency occurs only for Long signal (radial component of velocity). For blast wave oscillation analysis, it is only necessary to consider the low frequency oscillations [36; 37]. High frequency vibrations generally have no effect and should be classified just as white noise. The dependence of the dominant frequency on the distance is described in Figure 5.  
The dependence of the amplitude on the distance is described in Figure 6.  
As seen, the dominant frequency increases as the distance to the explosion center increases, as a power function, which can be described by the following equation: y = 1.0262x0.2622. The amplitude decreases as the distance to the explosion center increases, as a power function, which can be described by the equation: y = 18.139x\({}^{-2.276}\). Thus, it can be argued that there is a power-law dependence between the dominant frequency and the distance to the explosion center, as well as between the amplitude and the distance to the explosion center. It is worth noting that the dependence of dominant frequency increasing with distance contradicts the results in [26], which states that the dominant frequency decreases with distance. This contradiction is due to some differences in the experiment procedure. The experiments described in [26] were carried out underground  
Figure 5: Dominant frequency dependence on the distance. Figure 6: Amplitude dependence on the distance. with long distance (from 30 to 110 m) measurements and heterogeneous rock. The current experimental blasts were carried out on the surface of hard rock with preliminary soft soils excavation and short distance (up to 30 m) measurements close to the existing gas pipeline. The dominant increase can be explained by the soil vibration heterogeneity, as well as the close gas pipeline vibration impact. We assume the following reasons for the research results. It is possible that vibrational amplitude at higher frequencies could be underestimated due to the influence of the gas pipeline natural vibration occurring at the same frequencies, but with phase mismatch. At the same time, when the oscillation phases coincide, the amplitude rate may, however, increase. In all cases, any source of vibration close to the measurement point influences the resulting amplitude rate. The research results could be more comprehensive if, in addition to the measurements at certain points, the instruments were also applied directly on the pipeline to record its natural oscillations and other parameters showing the resonance clearly.