The association between ground gas radon variations and geologic activity in Hawaii

Abstract

Soil gas radon activities have been recorded at 10 stations on Kilauea volcano for approximately 5 years. Long‐term average radon activities were found to vary substantially among the sites monitored. Spatial variations appear to be controlled predominantly by (1) near‐surface hydrothermal activity, (2) thickness and permeability of soil cover, and (3) the presence of subsurface fracturing. Temporal changes in radon activity show minor correlation with meteorological changes but a strong correlation with seismic and volcanic events on Kilauea: magmatic intrusions were associated with contemporaneous changes in radon concentrations, whereas seismic events were associated with precursory radon anomalies. Such changes may be caused by release of trapped radon from rocks by microfracturing under broadly distributed stress changes associated with intrusion events and preceding seismic events.