Result of alpha track detection of radon in soil gas in the Khlong Marui Fault Zone, Southern Thailand: A possible earthquake precursor

Abstract

Measurements of radon concentration in soil gas were conducted at ten stations (ST1-ST10), located mainly in theKhlong Marui Fault Zone, Thap Put District, Phang Nga Province over a period from 28 January to 25 April, 2007. The resultsof the radon concentration were presented as the variation of cumulative alpha track over a week period. At Station ST10 theradon concentrations are in general higher than those at other stations for every week. Two significant radon anomalies werefound to have the concentration above the mean value plus one standard deviation. During the period of monitoring thelocal and regional earthquake activities were observed showing patterns consistent with the occurrence of the radon anomalies.The maximum radon concentration is interpreted to be related to a possible influence of the pressure and stress increasedin the subsurface. An increase in the number of earthquakes is observed correlating to a lower radon concentration when thesubsurface pressure dropped due to tectonic stress release by seismic activities. Therefore, it would be possible to use thevariation of soil gas radon concentration as an earthquake precursor in the Khlong Marui Fault Zone.

Keywords

• radon in soil gas
• alpha track
• earthquake precursor
• Khlong Marui Fault Zone