## 2 Region, Data, Method
### Seismic Noise Parameters  
To analyze spatiotemporal variations of seismic noise, time series of the daily values of four statistical parameters were used: generalized Hurst exponent \(\alpha^{*}\), singularity spectrum support width \(\Delta\alpha\), wavelet-based spectral exponent \(\beta\), and minimum normalized entropy of squared orthogonal wavelet coefficients \(En\) calculated for all stations during the 2011-2021 observation period [35; 36; 39]. The statistical parameters of seismic noise were estimated according to daily data of 1-min signal registration on BHZ channels for all stations (Figure 1, Table 1). To calculate the noise parameters, an updated archive of 1-min continuous recordings was created at 21 stations of the KB GS RAS formed from daily fragments of records with a frequency of 100 and 20 Hz by averaging them in a window of one minute (1440 min values in each day) ([[http://www.ceme.gsras.ru/new/infres/](http://www.ceme.gsras.ru/new/infres/)]([http://www.ceme.gsras.ru/new/infres/](http://www.ceme.gsras.ru/new/infres/)), accessed on 31 December 2021). Below is a brief description of the four seismic noise statistics used in this study. Multi-fractal parameters \(\Delta\alpha\) and \(\alpha^{*}\). Consider some random fluctuation \(x(t)\) on a time interval \([t-\delta/2,t+\delta/2]\) of length \(\delta\) centered at the time point \(t\). Consider the range \(\mu(t,\delta)\) of random fluctuations on this interval, that is, the difference between the maximum and minimum values:  
\[\mu(t,\delta)=max\ x(s)-min\ x(s), \tag{1}\]  
when \(t-\delta/2\leq s\leq t+\delta/2\). If we force \(\delta\to 0\), then the value \(\mu(t,\delta)\) will also tend to zero, but the speed of this decrease is important here. If the speed is determined by the law \(\delta^{h(t)}\): \(\mu(t,\delta)-\delta^{h(t)}\), or if there is a limit \(h(t)=\lim\limits_{\delta\to 0}\frac{\log(\mu(t,\delta))}{log(\delta)}\), then the \(h(t)\) is called the Holder-Lipschitz exponent. If the value \(h(t)\) does not depend on the moment of time \(t\): \(h(t)=const=H\), then the random fluctuation \(x(t)\) is called mono-fractal, and the value \(H\) is called the Hurst exponent. If the Holder-Lipschitz exponents \(h(t)\) differ for different moments of time \(t\), then \begin{table}
\begin{tabular}{c c c c c c} \hline
**Station Groups Influence Factors*** & **All Stations, N= 21 (100\%)** & **Northern, N = 5 (100\%)** & **Central, N = 7 (100\%)** & **Southern, N= 9 (100\%)** & **Non-Volcanic, N = 15 (100\%)** \\ \hline coastal, n (\%) & 11 (52\%) & 3 (60\%) & 2 (29\%) & 6 (67\%) & 10 (67\%) \\ \hline volcanic, n (\%) & 6 (29\%) & – & 4 (57\%) & 2 (22\%) & – \\ \hline \end{tabular}
* n denotes the number of stations and the \% of the total number of stations in group N is indicated in brackets.  
\end{table} 
Table 2: Distribution of stations into groups, taking into account the number of stations affected by sea waves (coastal stations) and volcanic activity (volcanic stations). the random fluctuation is called a multi-fractal, and the notion of a singularity spectrum \(F(\alpha)\) can be defined for it [40]. To do this, we select a set \(C(\alpha)\) of such moments of time \(t\) that have the same value \(\alpha\) as the Holder-Lipschitz exponent: \(h(t)=\alpha\). For some values \(\alpha\) the set \(C(\alpha)\) is not empty, that is, there are some minimum \(\alpha_{min}\) and maximum \(\alpha_{max}\), such that only for \(\alpha_{min}<\alpha<\alpha_{max}\) does the set \(C(\alpha)\) contain some elements. The multi-fractal spectrum of a singularity \(F(\alpha)\) is the fractal dimension of a set of points \(C(\alpha)\). The parameter \(\Delta\alpha=\alpha_{max}-\alpha_{min}\), called the singularity spectrum support width, is an important multi-fractal characteristic. In addition, of considerable interest is the argument \(\alpha^{*}\) that provides the maximum of the singularity spectrum: \(F(\alpha^{*})=max\,F(\alpha)\),when \(\alpha_{max}\geq\alpha\geq\alpha_{min}\), called the generalized Hurst exponent.