MONITORING OF SUBSOIL VOLUMETRIC RADON (222RN) ACTIVITY IN THE PARATUNKA GEOTHERMAL SYSTEM IN 1997-1998: IMPLICATIONS FOR USING IT AS A PRECURSOR OF LARGE EARTHQUAKES IN KAMCHATKA

Abstract

Monitoring of subsoil volumetric radon activity in the Paratunka geothermal field began in late October 1997. The aim of this work was to find correlation between the Rn behavior and the geodynamic environment in Kamchatka. During a period of October 1997 to November 1998, the time of writing this paper, our team investigated the effects of air-pressure fluctuations and seasonal air-temperature variations on the dynamics of volumetric radon behavior to eliminate these meteorological effects. We found an obvious correlation between the seismotectonic situation in the area and the volumetric radon activity. The high disturbance in the radon behavior recorded in November 1997 correlated with a transient earth strain wave which might have been caused by a change in the Earth's rotation produced by a rearrangement in the global atmospheric circulation as a result of a powerful solar flare on November 4, 1997. The dynamics of the radon activity reflected the effect of the solar flare, via the atmosphere, on the Earth's lithosphere, which might have triggered a release of stresses stored in the lithospheric plates bordering Kamchatka. Two K > 12 earthquakes that occurred in the Gulf of Avacha 140 km from the observation site were preceded by abnormal disturbances in the radon behavior, which were interpreted as earthquake precursors. Disturbances in the radon behavior were also recorded before deep (H > 100 km) earthquakes with K > 12. A plan was proposed for deploying a network of stations for monitoring volumetric radon activity to tackle problems of geodynamics and large earthquake prediction in the Gulf of Avacha region.