A nonlinear technique was used to analyse soil radon concentrations measured over a year and four months in Jiaosi, northeast Taiwan, to find precursory signals for regional earthquakes. The recorded data demonstrated that numerous meteorological and geophysical parameters influence radon gas emission from the soil, resulting in a complex soil radon time series. Empirical Mode Decomposition (EMD) was used to remove periodic factor components before applying the Hilbert-Huang Transform (HHT) to find pre-seismic anomalies. The discovered anomalous variations were associated with regional earthquakes of magnitude 5 or more that occurred within 100 km of the monitoring site. The effect of precipitation on soil radon emissions has also been discussed. The results show that the adopted technique can be used to analyse radon concentrations in soil gas for the prediction studies of regional earthquakes. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Earth Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)