title: Normal seasonal variations for atmospheric radon concentration: a sinusoidal model.
abstract: Anomalous radon readings in air have been reported before an earthquake activity. However, careful measurements of atmospheric radon concentrations during a normal period are required to identify anomalous variations in a precursor period. In this study, we obtained radon concentration data for 5 years (2003-2007) that can be considered a normal period and compared it with data from the precursory period of 2008 until March 2011, when the 2011 Tohoku-Oki Earthquake occurred. Then, we established a model for seasonal variation by fitting a sinusoidal model to the radon concentration data during the normal period, considering that the seasonal variation was affected by atmospheric turbulence. By determining the amplitude in the sinusoidal model, the normal variation of the radon concentration can be estimated. Thus, the results of this method can be applied to identify anomalous radon variations before an earthquake.
authors.affiliation: Kobe Pharmaceutical University, 4-19-1, Motoyamakitamachi, Higashinada-ku, Kobe 658-8558, Japan.
authors.forename: Koseki
authors.initials: K
authors.lastname: Hayashi
authors.affiliation: Kobe Pharmaceutical University, 4-19-1, Motoyamakitamachi, Higashinada-ku, Kobe 658-8558, Japan. Electronic address: yasuoka@kobepharma-u.ac.jp.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Yasuoka
authors.affiliation: Tohoku University, 6-3, Aza Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nagahama
authors.affiliation: Tohoku University, 6-3, Aza Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Muto
authors.affiliation: Fukushima Medical University, 1, Hikarigaoka, Fukushima 960-1295, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Ishikawa
authors.affiliation: Fukushima Medical University, 1, Hikarigaoka, Fukushima 960-1295, Japan.
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Omori
authors.affiliation: Fukushima Medical University, 1, Hikarigaoka, Fukushima 960-1295, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: Fukushima Medical University, 1, Hikarigaoka, Fukushima 960-1295, Japan.
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Homma
authors.affiliation: Kobe Pharmaceutical University, 4-19-1, Motoyamakitamachi, Higashinada-ku, Kobe 658-8558, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Mukai
mesh_terms: D008962:Models, Theoretical; D011834:Radiation Monitoring / Q000379:methods*; D011886:Radon / Q000032:analysis*; D012621:Seasons
chemical_list: D011886:Radon
keywords: Atmospheric radon; Atmospheric turbulence; Seasonal variation; Sinusoidal model