Measurements of soil radon in south Russia for seismological application: Methodological aspects

As a first step in the monitoring of soil radon in search of harbingers of earthquakes, an investigation of suitable measurement techniques was conducted. As a result of these investigations, the following recommendations are made. Semiconductor and scintillation (ZnS) counters are the most suitable for Rn monitoring with chambers for natural drift of emanations to the detector. The method of compulsory selection of soil air is hardly effective. Soil aerosols might enter the drift chamber; these aerosols transfer many radioactive isotopes. The most suitable locations for placement of detectors of radon are cellars. Measurements should be continuous in character. The choice of a place for monitoring near mud volcanoes and faults should be determined by an Rn survey. In mud volcanoes, the best locations are areas with an average concentration of radon. For faults, identical tendencies of change in radon are maintained at some distance from the borders of the fault. For large faults, this distance is equal to half the width of the fault. For small faults, this distance increases by up to 3 times the fault width. All the recommendations were applied in the Northern Caucasus. Reliable results of the changes in soil radon were obtained during strong geophysical processes.

► An investigation of Rn measurement as earthquakes harbingers was conducted.
► Semiconductor and scintillation counters with drift of emanations are the suitable.
► Measurements should be continuous in character.
► The choice of a place for monitoring should be determined by an Rn survey.