The origin and detection of spike-like anomalies in soil gas radon time series

Abstract

Desorption of radon is of short duration but longer than telluric noises and is usually accomplished in less than one minute based on our binary event counting with a 16 second interval. Adapting an hourly counting time schedule, telluric noises as well as transient variation of radon anomalies of a few hours duration can be excluded but not the spike-like anomalies of a few minutes duration. The time series of soil gas radon, as recorded continuously in a redesigned ditch located inside an active fault zone, has sporadic spike-like anomalies. The anomalies could represent desorbed radon from shallow sources as observed from a similar detecting system located near a construction site. Radon release due to compressive stress is related to compressive back-filling activities. Spike-like anomalies, on the other hand, are related to caisson auguring shear activities. Charge transfer related to electrokinetic potential phenomena may have resulted in the sudden radon releases and caused spike-like anomalies. The timing of the anomalies provides good information on the timing of electokinetic potential change as a result of outward propagation of stress from hypocenter. With multiple monitoring stations, the location, timing, and magnitude of the incoming earthquake can then be calculated or graphically derived.

Fractal Analysis of Pre-Seismic Electromagnetic and Radon Precursors: A Systematic Approach

“…Most importantly, according to [16,27,43,44] , the radon anomalies of the earthquake 33 of Table 2, were not detected only with active techniques but also through passive ones. It is significant to note also, that in the radon related earthquake literature, the methods that are used for processing the radon signals are, mostly, statistical or visual [46,[75][76][77][78][79].…”

A possible link between radon anomaly and earthquake

“…The stress centers form strain fields and stress gradients of diminishing magnitude towards the periphery. These pre-earthquake stress gradients move underground fluids, carrying some dissolved gases such as radon, helium, methane, carbon dioxide, nitrogen etc., to the subsurface region, mainly through faults, lineaments and thermal areas, which are highly permeable pathways for soil-gas (Yang et al, 2003(Yang et al, , 2006Chyi et al, 2005Chyi et al, , 2010Chyi et al, , 2011Fu et al, , 2008Walia et al, 2005aWalia et al, , 2005bWalia et al, , 2008Walia et al, , 2009Walia et al, , 2010Choubey et al, 2007;Yang, 2008;Montazeri et al, 2011;Woith et al, 2011). So subsoil radon anomaly is observed in the soil-gas measurements at or near a fault and/or a lineament before and after an earthquake.…”

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.…”