Recent progress in radon-based monitoring as seismic and volcanic precursor: A critical review

Optimization of dissolved Radon monitoring in groundwater to contribute to the evaluation of the seismic activity: an experience in central-southern Italy

“…2B, C, the dissolved Rn concentrations appear to be variable around the average values of 20,068.83 and 5038.3 Bq/m 3 , respectively. However, it is possible to observe seasonal variations or rapid changes in Rn content commonly linked to the hydrogeological and hydrological cycles [22]. Figure 2A shows the background seismicity of the study area (available online: http://terre moti.ingv.it/), which was recorded in the same period of the gas-geochemical monitoring.…”

“…However, despite these studies, there are still several significant gaps in adopting Rn as an earthquake precursor. According to a previous study [22], there are many reasons for poor understanding of possible precursor activity, such as inadequate statistical evidence, the lack of long-term measurements and the difficulty in distinguishing between seasonal variations and anomalies at the same magnitude. Acquiring a solid understanding of the chemical and physical processes occurring in the Earth's upper crust requires a substantial number of measurements.…”

From Sensor to Cloud: An IoT Network of Radon Outdoor Probes to Monitor Active Volcanoes

“…Since then, many studies have been conducted on Mount Etna (see, for instance, [ 2 , 3 ] and references therein) and on many other volcanoes [ 4 ] to assess the potential of radon as precursor of volcanic activity. Radon gas emissions in soils have been monitored continuously, and correlations with volcanic or tectonic events have been repeatedly observed [ 5 ]. However, because of the complexity of the radon transport mechanism, these correlations need more investigations [ 6 ].…”

“…Etna, airborne radon activity measured on the volcano flanks are typically of a few tens of Bq/m 3 [ 7 ]. Contrastingly, radon activity in soil gases in active areas is generally higher than 1000 Bq/m 3 and can reach several tens of kBq/m 3 (see [ 3 , 5 ], for instance). Since the radon activity to be measured in the air is low to moderate, the response time of any radon measurement instrument will be much higher than in the context of soil gas studies, and as a consequence, time resolution will be poorer.…”

Stochastic Models for Radon Daily Time Series: Seasonality, Stationarity, and Long-Range Dependence Detection

“…For instance, climate or tidal forces reflect in a multiple seasonality of the radon time series: hourly, diurnal, multi-day, annual, and even multi-annual cycles have been detected in different studies worldwide (Crockett et al, 2006;Udovičić et al, 2014;Yan et al, 2017;Crockett et al, 2018;Siino et al, 2019b;D'Alessandro et al, 2020). Of particular interest is the role of Rn as a potential earthquake precursor (Barbosa et al, 2015;Woith, 2015;Baskaran, 2016;Morales-Simfors et al, 2019) because the fracturing processes in the crust could enhance the mobility of Rn toward the surface (Toutain and Baubron, 1999;Woith, 2015). Similarly, anomalies can be the result of weather episodes which cannot be explained by meteorological variables.…”