Radon anomalies and microearthquakes at Lake Jocassee, South Carolina

Abstract

Continuous low‐level seismic activity was found to occur at Lake Jocassee after the impoundment of the reservoir in 1975. In addition to monitoring seismic activity we began (in January 1976) a series of geochemical measurements in an effort to search for precursors to ML ∼ 2–2.5 events. Discrete water samples were collected from wells and a spring, and their radon content was determined by scintillation counting. These data were comparable to those obtained from a continuous Rn monitor in the spring using an ionization chamber. Soil Rn measurements in track etch cups were started in 1977. The results of the data collected so far indicate (1) that long‐term fluctuations occur in the radon concentrations in the spring water with a period of ∼44 weeks (the radon content being 50–100% lower in summer and fall), (2) that anomalous changes in the radon concentrations have occurred both before and after earthquakes, the timing of the anomaly being dependent on the distance of the epicenter to the radon sample site, (3) that both high and low anomalous radon values occur, and (4) that the soil randon method using track etch cups is useful in determining areas of high and low Rn concentration but not for a study of short‐term temporal changes.

Geochemical precursors to seismic activity

“…Recent monitoring programs have typically employed intermittent sampling from natural springs, shallow groundwater wells, or deep (2000m) monitoring wells, and have determined radon concentrations using gas-phase scintillation counting or liquid/liquid extraction of radon and liquid scintillation counting (FRIEDMANN and HERNEGGER, 1978;TALWANI et a/., 1980;TENG, 1980TENG, , 1984WAKITA et a/., 1980aWAKITA et a/., , 1985HAUKSSON, 1981a;HAUKSSON and GODDARD, 1981;ALLEGRI et a/., 1983;CHUNG, 1985;FRIEDMANN, 1985;KING, 1985aKING, , 1986LIV eta/., 1985;SHAPIRO eta/., 1985;SANTOYO et a/., 1987). Continuous monitoring of radon activities is now becoming a more accepted method, as the earlier results have shown that radon anomalies are frequently of short duration.…”

“…The apparent durations of the radon anomalies ranged from a few hours, using the semiconductor detectors (KING, 1985b), to periods of weeks or months (FLEISCHER and MOGRO-CAMPERO, 1985;. Anomaly amplitudes have ranged from an increase of a factor of two above prior backgrounds TALWANI et a/., 1980;STEEL, 1981STEEL, , 1985ABDUVALIYEV eta/., 1984) to increases of factors often or greater (KING, , 1985bMOGRO-CAMPERO et a/., 1980;. In one case (FLEISCHER and MoGRO-CAMPERO, 1985), decreases in radon activity by factors of more than 500 were attributed to seismic effects.…”

Earthquake Prediction Studies Using Radon as a Precursor in N-W Himalayas, India: A Case Study

“…This evidence stimulated research work in this area soon afterwards in many countries. Radon observations, both in soil-gas and in groundwater, revealed many precursory changes in its concentration before an earthquake (Talwani et al 1980;Mogro-Campero et al 1980;Fleischer 1981;Liu et al 1984/85;Virk 1986Virk , 1993Virk , 1997Segovia et al 1989;King et al 1993;Virk and Singh 1992;Igarashi et al 1995;Heinicke et al 1995;Singh et al 1999;Chyi et al 2005;Yang et al 2005). Due to such observed correlation, radon is considered as one of the few promising precursors that can be used for earthquake prediction studies.…”

Radon and helium anomalies in mud volcanoes from northern Apennines(Italy). A tool for earthquake prediction.

“…have been widely discussed (see e.g. Mogro Campero et al, 1980;Talwani et al, 1980;King, 1980King, , 1985Teng 1980;Hauksson, 1981;Barsukov et al, 1984;Friedmann, 1985). The conclusions which have been drawn, however, are not univocal, but in some cases con tradictory, as they vary with the nature of the precursor (free gas, gas or solid dissolved in water) and of the considered system.…”