Occurrence of anomalies in soil radon volume activity before tectonic earthquakes

Abstract

Research subject. Earthquakes are a global problem for the entire world population. Therefore, a search for ways to predict and prevent tectonic events is a highly relevant task. Despite the existence of controversial opinions on the possibility of predicting tectonic earthquakes, research in this direction continues. Among numerous possible precursors of earthquakes, anomalies in the volume radon activity (VRA) are the most physically justifed ones. The aim of this research was to compare the observed anomalies of soil radon with the recorded seismic events in order to fnd common patterns. The research area was the Kuril Islands. VRA monitoring was conducted at the South Kuril Geophysical Station of the Institute of Marine Geology and Geophysics of the Far Eastern Branch of the Russian Academy of Sciences.

Methods and materials. Measurements were carried out in the advective mode: soil air from a depth of 70 cm was forcibly delivered to the detector using a pump. For a retrospective analysis, we took registered seismic events with a magnitude greater than 4 that occurred within a radius of 500 km from the monitoring station in Yuzhno-Kurilsk during 2011–2018. Statistical data were processed using Microsoft Excel, Statistica software. Results. A method for comparing radon anomalies and earthquakes was developed. Using the developed methodology, it was found that the geodynamic criterion of ≥2 (the ratio of earthquake magnitude to logarithm of distance from event epicenter to the monitoring station in km) can be used when comparing VRA anomalies with tectonic earthquakes. Out of the 166 considered tectonic earthquakes meeting the geodynamic criterion of ≥2.148, the events were preceded by VRA anomalies. The position of the earthquakes was determined relative to the extremum of previous anomalous radon values in the time interval. Eac  of the considered earthquakes meeting the geodynamic criterion ≥2, which had been preceded by a radon anomaly, occurred either after its extremum or coincided with it in time. Conclusions. The manifestation of tectonic earthquakes in VRA anomalies after passing the extremum can be considered as a short-term prognostic criterion and be used for distinguishing between “near” and “far” events.