Soil Gas Radon Spectra and Earthquakes

Abstract

Continuous soil gas radon monitoring in real time with improved solidstate detector is carried out in south-central and southern Taiwan. The time series register spike-like anomalies which could be precursors of earthquakes. Monitoring stations located in a brecciated zone of active fault at Taiwan 3 and faults at Taiwan 1 showed drastic variations of radon when the terrain is stressed before the onset of earthquake. In contrast, the spectrum recorded at a station sited on a craton Akron 1 which is sited on a craton shows no significant radon variations. To actually prove that the variation of the time series is related to stress, a fourth station was anchored in a sand column (209 L) with exactly the same type of radon detector system. The time series recorded in this manner shows higher background level and spikes of high radon counts as it is stressed. Temperature and moisture variations are not affecting radon counts.

Methane Venting in Gas Hydrate Potential Area Offshore of SW Taiwan: Evidence of Gas Analysis of Water Column Samples

“…Variations of radon concentrations have been widely interpreted as a useful precursor of earthquake and magmatic activity (e.g., Segovia et al 2003;Chyi et al 2005;Cigolini et al 2005;Walia et al 2005b;Yang et al 2005b;Imme et al 2006). We can observe higher radon concentrations wherever there is a higher flux of carrier gases at fault zones or hydrothermal areas.…”

Hydrochemical Changes in Spring Waters in Taiwan: Implications for Evaluating Sites for Earthquake Precursory Monitoring

“…In the past, substantive evidence in support of many diverse kinds of precursors, including hydrological and chemical changes in subsurface fluids prior to or at the same time as a large earthquake, has been found. Among these are valuable, insightful precursory changes in gases involved in both hydrothermal processes, like Rn, He, CO 2 , CH 4 , H 2 , Ar and N 2 , and in water chemistry, like Cl − , F − , NO 3 − and SO 4 2− (Hauksson 1981;King 1986;Tsunogai andWakita 1995, 1996;Sugisaki et al 1996;Toutain et al 1997;Chyi et al 2005;Italiano et al 2005;Ramirez-Guzman et al 2005;Walia et al 2005;. Such geochemical anomalies are generally associated with changes in a subsurface water circulating system in the process of earthquake generation (Thomas 1988;Rojstaczer and Wolf 1992;Muir-Wood and King 1993;Rojstaczer et al 1995;Sugisaki et al 1996).…”

Preseismic anomalies in soil-gas radon associated with 2016 M 6.6 Meinong earthquake, Southern Taiwan

“…1). Selected fault zones are categorized as active faults zones by Central Geological Survey of Taiwan and may be considered as conducive for earthquake precursory studies in Taiwan (e.g., Chyi et al 2001Chyi et al , 2005Chyi et al , 2011Fu et al 2005Fu et al , 2008Fu et al , 2009Fu et al , 2017aYang et al 2005Yang et al , 2011Walia et al 2009aWalia et al , b, 2013. To build a monitoring station, reconstructions were done by digging holes of approximately 2.5 m and by casing these holes with PVC pipes.…”