The purpose of this research phase is to study the relationship between the radioactivity of groundwater in the southern Angara region and the seismic situation in the region. To identify and study this dependence, daily monitoring of the content of radon radioactive gas in groundwater in a reference source and periodic measurements in 7 other water supply systems were organized. Based on the results of operational observations, an array of numerical data was obtained, including information on the energy classes (K) of seismic events that occurred within the Baikal region and fluctuations in the concentration of dissolved radon (Q) in the base of the studied water sources. The resulting material is characterized by a unified methodological and metrological basis with nine-year monitoring organized in the territory in 2012 and is suitable for use as a basis for further research. A weak inverse statistical relationship between the Q and K parameters and a moderate direct effect of seismicity on subsequent bursts of radon activity were revealed. At the same time, the “delay” of the reaction of the emanation field was approximately four days. In addition, evidence of the existence of a relationship between the considered parameters was a decrease in the volumetric activity of radon by 15-20% in all studied water phenomena after the largest seismic events in the region that occurred during the testing period. An important feature is that the distances at which the response of the emanation field was recorded exceeded the calculated values in all cases. Of the known models of fluctuations of the Q parameter associated with the preparation of seismic events, the greatest convergence in relation to the original results was shown by the model proposed by Kuo T [Groundwater, 2014]. In the extension zone of the Baikal rift, according to the Kuo model, the preparation of deformation takes place in three stages, in the first of which the concentration of dissolved radon is unchanged, in the second it decreases, and in the third it returns to its original values. The difference lies in the fact that within the Southern Angara region there is a “delay” in the reaction of the emanation field, and after the event, the intensity of emanations increases for some time. The preliminary results presented in the article allow relying on the identification of short-term precursors of strong earthquakes in the South Baikal region, which is distinguished by the most developed infrastructure in the Baikal region.

Seminsky Aleksandr Konstantinovich, Candidate of Sciences (Geology and Menerology), Junior Researcher, Institute of the Earth's Crus SB RAS, 128, Lermontov st., Irkutsk, 664033, Russian Federation, e-mail: zzzsancheszzz@gmail.com 

Seminsky Konstantin Zhanovich, Doctor of Sciences (Geology and Menerology), Head of Laboratories, Institute of the Earth's Crust SB RAS, 128, Lermontov st., Irkutsk, 664033, Russian Federation; Irkutsk Scientific Center SB RAS, 134, Lermontov st., Irkutsk, 664033, Russian Federation, e-mail: seminsky@crust.irk.ru

Seminsky A.K., Seminsky K.Zh. Preliminary Results of the Study of the Relationship of Seismic Activity with the Concentration of Radon in Groundwater in the Southern Angara Region. The Bulletin of Irkutsk State University. Series Earth Sciences, 2020, vol. 33, pp. 100-111. https://doi.org/10.26516/2073-3402.2020.33.100 (in Russian)

Baikalskii filial geofizicheskoi sluzhby [Baikal branch of geophysical service]. Available at: http://seis-bykl.ru/ Main event directory (date of access: 10.05.2020) (in Russian)

Kozlova I.K., Urkov A.K. Metodicheskie izmereniya soderjaniya radona-222 v pochvennom vozduhe pri monitoringovih nabludeniyah [Methodological issues of measuring the content of radon-222 in soil air during monitoring observations]. Yralskiy geofizicheskiy vestnik [Ural Geophysical Bulletin], 2005, no. 7, pp. 31-34 (in Russian)

Utkin V.I., Mamirov E., Kann M.V., Krivasheev S.V., Yurkov A.K., Kocakin I.I., Shiskanov A.N. Monitoring radona pri izychenii prochessa podgotovki tektonichesrjuj zemletryaseniya na severnom Tyan-Shane [Radon monitoring in the study of the process of preparing a tectonic earthquake in the northern Tien Shan]. Fizika Zemli [Earth Physics], 2006, no. 9, pp. 61-70. (in Russian)

Seminskiy K.Zh., Seminskiy A.K. Radon v podzemnyih vodah Pribaykalya i Zabaykalya: prostranstvenno-vremennyie variatsii [Radon in the underground waters of the Baikal and Trans-Baikal region: space-time variations]. Geodinamika i tektonofizika [Geodynamics and tectonophysics], 2016, vol. 7, no. 3, pp. 477-493. (in Russian)

Dobrovolsky I.P., Zubkov S.I., Miachkin V.I. Estimation of the size of earthquake preparation zones. Pure Appl. Geophys., 1979, vol. 117, pp. 1025-1044.

Fleischer R.L. Dislocation model for radon response to distant earthquakes. Geophys. Res. Lett., 1981, vol. 8, pp. 477-480.

Fleischer R.L., Mogro-Campero A. Association of subsurface radon changes in Alaska and the northeastern United States with earthquakes. Geochim. Cosmochim. Acta, 1985, vol. 49, pp. 1061-1071.

Ghosh D., Deb A., Ranjan S., Haldar S., Sengupta R. Radon as seismic precursor: new data with well water of Jalpaiguri, India. NatHazards, 2011, vol. 58, pp. 877-889. 

Hauksson E. Radon content of groundwater as an earthquake precursor: evaluation of worldwide data and physical basis. J. Geophys. Res., 1981, vol. 86, pp. 9397-9410.

Hirok C., Waseem B, Naseer I., Rakaesh K., Debasis G., Prasanta S., Bikash S. Long range gas-geochemical anomalies of a remote earthquake recordedsimultaneously at distant monitoring stations in India. Geochemical Journal, 2011, vol. 45, pp. 137-156. 

King C.-Y. Episodic radon changes in subsurface soil gas along faults and possible relation to earthquake. Journal of Geophys. Research, 1980, vol. 85, no. 6, pp. 3065-3078.

King C.-Y., Walkingstick C., Basler D. Radon in soil gas along active faults in Central California. Field studies of radon in rock, soil and water: U.S. Geological survey bulletin. Gunderon L. and Wanty R. (eds.). 1991, pp. 77-133.

Kuo T. Correlating Precursory Declines in Groundwater Radon with Earthquake Magnitude. Groundwater, 2014, vol. 52, no. 2, pp. 217-224.

Morgounov V.A., Malzev S.A. A multiple fracture model of pre-seismic electromagnetic phenomena. Tectonophysics, 2007, vol. 431, pp. 61-72.

Rikitake T. Earthquake prediction: an empirical approach. Tectonophysics, 1988, vol. 148, pp. 195-210.

Seminsky К.Zh., Bobrov А.А. The first results of studies of temporary variations in soil­radon activity of faults in Western Pribaikalie. Geodynamics & Tectonophysics, 2013, vol. 4, no. 1, pp. 1-12. https://doi.org/10.5800/GT-2013-4-1-0088.

Toutain J.-P., Baubron J.-C. Gas geochemistry and seismotectonics: a review. Tectonophysics, 1999, vol. 304, pp. 1-27.

Virk H.S. A critique of empirical scaling relationship between earthquake magnitude, epicentral distance and precursor time for interpretation of radon data. J. Earthquake Prediction. Res., 1996, vol. 5, pp. 547-583.

Woith H. Radon earthquake precursor: a short review. Eur. Phys. J. Special Topics, 2015, vol. 224, pp. 611-627.