Seismic activity-related anomaly detection in Soil Radon Emanation

Soil Radon Emanation has been continuously monitored along with other geophysical measurements in the seismically active Marmara region of Turkey over the past ten years for understanding the pre-earthquake crustal deformation. In this paper, radon gas emanation time series are decomposed into intrinsic (characteristic) modes via Empirical Mode Decomposition (EMD) and the relationship between seismic activities and radon gas emanation is investigated. A statistical model of gas emanation is discussed. Also, observation of the atmospheric effects as daily-quasi-periodic fluctuations (which may sometimes dominate the recordings) is demonstrated and a signal-adaptive periodicity removal process based on the EMD method is used for robust processing. The results for both seismic and a-seismic time intervals and a short discussion on how the analysis of radon gas data can be used as a precursor of seismic activity is presented.