4:10 PM - 4:30 PM
[MIS08-15] Radon Monitoring in the Gulf of Corinth, Greece
★Invited Papers
Keywords:Radon monitoring, pre-earthquake phenomena, earthquake precursors
Significant new findings on the relation between soil radon variations with the natural seismicity and forthcoming events have been obtained after continuous real-time monitoring of soil radon concentration in the area of the Gulf of Corinth, Greece through a five-year period. The Gulf of Corinth, one of Earth's most active continental rift systems is a high seismic hazard area with many catastrophic earthquakes in its history; however its seismicity rate is not as high comparing to others active tectonic systems such as the Hellenic Arc region. The long quiescent periods between the major seismic events essentially help to establish a safe correlation of possible pre-earthquake radon variations with the seismic events. The Gulf of Corinth has a high rate of crustal extension of up to 1.5 cm/yr at the western part and 0.5 at the eastern one.
Two permanent real-time and continuously operating gamma-ray spectrometers have been installed in the area as a part of a larger network of radon monitoring stations covering South and Western Greece. More specifically, in order to observe pre-earthquake anomalies in radon concentration before strong earthquakes we have installed soil radon concentration monitoring stations at high seismicity areas such as the Hellenic arc in Western Greece and the eastern part of the Gulf of Corinth. The installation of the stations began in May 2016 and in all sites a real-time monitoring was established. The network is currently expanding with new stations at Crete.
The radon network was mainly based on NaI(Tl) scintillation detectors for γ-spectrometry. A full spectrum analysis processing that is applied to the data, provides us with a good energy resolution. At all stations there is detailed information of meteorological parameters that could affect the radon concentration measurements such as temperature, pressure, humidity and wind speed.
The Loutraki station, which is installed at a site close to a large fault with significant hydrothermal flux, provided us with highly interesting insights about the correlation of the seismicity rate with radon level at the area. However, an even more noteworthy observation is that the radon level variations also seem to follow a pattern, related to the stronger events. This station shows a very high consistency in the measurements and is strongly insulated from exogenous factors such as temperature, pressure and humidity.
Our results appear to be compatible with the “dilatancy model” that proposes an inelastic volumetric increase of rocks prior to failure. Before earthquakes there is accumulation of tectonic strain that produces a slow, steady increase of effective stress.
Before the major events there is a steady and slow increase of radon due to the increase of cracks and porosity and/or an increase in the flow rate of pore water. In addition, before strong events there is a significant drop of radon level.
Several seismic events have been associated with soil radon variations in three local radon monitoring stations.
Two permanent real-time and continuously operating gamma-ray spectrometers have been installed in the area as a part of a larger network of radon monitoring stations covering South and Western Greece. More specifically, in order to observe pre-earthquake anomalies in radon concentration before strong earthquakes we have installed soil radon concentration monitoring stations at high seismicity areas such as the Hellenic arc in Western Greece and the eastern part of the Gulf of Corinth. The installation of the stations began in May 2016 and in all sites a real-time monitoring was established. The network is currently expanding with new stations at Crete.
The radon network was mainly based on NaI(Tl) scintillation detectors for γ-spectrometry. A full spectrum analysis processing that is applied to the data, provides us with a good energy resolution. At all stations there is detailed information of meteorological parameters that could affect the radon concentration measurements such as temperature, pressure, humidity and wind speed.
The Loutraki station, which is installed at a site close to a large fault with significant hydrothermal flux, provided us with highly interesting insights about the correlation of the seismicity rate with radon level at the area. However, an even more noteworthy observation is that the radon level variations also seem to follow a pattern, related to the stronger events. This station shows a very high consistency in the measurements and is strongly insulated from exogenous factors such as temperature, pressure and humidity.
Our results appear to be compatible with the “dilatancy model” that proposes an inelastic volumetric increase of rocks prior to failure. Before earthquakes there is accumulation of tectonic strain that produces a slow, steady increase of effective stress.
Before the major events there is a steady and slow increase of radon due to the increase of cracks and porosity and/or an increase in the flow rate of pore water. In addition, before strong events there is a significant drop of radon level.
Several seismic events have been associated with soil radon variations in three local radon monitoring stations.