## 1 Introduction  
Universal methods allowing highly accurate forecasts of the time of seismic shocks have been researched for over four decades in Europe [1, 2, 3, 4] and around the world [5, 6, 7, 8, 9, 10, 11, 12]. The research methodology and modeling of geodynamic phenomena have so far been based on the identification (including comprehensive analysis) of the behavior of geochemical precursors: \({}^{222}\)Rn, CO\({}_{2}\), He, H\({}_{2}\), CH\({}_{4}\), N\({}_{2}\), Ar, Pb, Cl, and SO\({}_{4}\)[13]. The most promising precursor is radon, which is present in water [14, 15, 16, 17], soil air [18, 19, 20], and the atmospheresof closed, isolated objects located in fault zones [21; 22] or underground research observatories [23; 24; 25; 26]. The use of radon in geophysical research consists of observations of the anomalous behavior of this gas, which typically occurs in short, usually hourly time intervals, as large fluctuations in its activity concentration. In the vast majority of cases, such anomalous behavior manifested as a sudden increase or decrease in radon concentration values is due to meteorological phenomena, such as atmospheric temperature and pressure, rainfall (mainly heavy), and wind force and direction [27; 28; 29; 30; 31]. These factors cause the concentration of \({}^{222}\)Rn activity to be subject to temporal fluctuations, with a clearly visible seasonal or cyclical trend that is independent of seismic activity. Based on such observations, the identification of changes (including anomalies) induced solely by seismic activity requires the decomposition of the radon signal and filtering of data representing seasonal or cyclical trends [1; 28; 32; 33; 34; 35]. Similar regularities were also observed as a result of studies conducted continuously since 2014 on the interaction of the radon signal and the geodynamic signal in the system of faults present in the space of the underground Geodynamic Laboratory of the Space Research Center of the Polish Academy of Sciences (GL SRC PAS) located under the Ksiaz Castle in Walbrzych, Poland [24]. The results of early research performed at this site [36; 37; 38; 39; 40; 41; 42; 43] confirmed that changes in the stress state in the rock mass due to tectonic activity (changes in the compression--extension phases) cause fluctuations in radon exhalation from rocks into the air filling the GL SRC PAS excavations. This phenomenon is manifested by changes in the concentration of \({}^{222}\)Rn activity in the air present in the excavations. These changes have nearly identical characteristics as a function of time at all measurement points, indicating that they occur within the entire volume of the rock mass in the analyzed area. Gas is exchanged between the lithosphere and atmosphere in excavations not only through active fault zones but also through the entire fractured surface of the rocks forming the roof, floor, and sidewalls of underground excavations [24]. The objective of this study was to identify the nature of statistically significant positive or negative interactions between geodynamic and radon signals observed during seismic events. The results are expected to be an important step towards identifying the similarities and differences in the signals recorded by measurement instruments before and after a seismic shock. Ultimately, they allow the nature of the interaction to be linked to the phases of tension or compression of the rock mass occurring at a given time before and after an event. The authors hope that the results will contribute to improving earthquake forecast methods, which are of great importance, especially in densely populated seismic areas. In light of the well-documented analyses in the literature focusing on the relationship between geochemical and tectonic changes, this study examined the correlation between rock mass deformation and variations in radon activity concentration, taking into account four selected seismic events of tectonic origin.