The relationship between the number of daily earthquakes (M\(\ge 5)\) in the world and the daily Be-7 concentrations in the surface air at each of 69 stations in the world from September 9, 2001, to December 31, 2017, was statistically analyzed. Aftershocks were not included in the analysis. The number of certified radionuclide stations increased from 5 in 2001 up to 69 in 2017.
(1) The median of the numbers (\(n\)) of daily earthquakes (M\(\ge\)5) in the world during the period was 3. Therefore, the observation days of the Be-7 concentrations of each station were classified by \(n\ge 4\)or \(n\le 3.\)The number of stations where the median of the Be-7 concentrations of each station on days of \(n\ge 4\) was greater was 43, and the number of stations where the median of the Be-7 concentrations of each station on days of\(n\ge 4\) were smaller than or equal to that on days of \(n\le 3\)was 26. In more stations (significantly \((p=0.0147)\) by the binomial test), the median of the Be-7 concentrations of each station on days of \(n\ge 4\) was greater than that on the days of \(n\le 3\). In 14 years of total 17 years, in more stations, the median of the Be-7 concentrations of each station on days of \(n\ge 4\) were greater than that on the days of \(n\le 3\).
(2) For r = 1 ~ 12 and 15, the observation days were classified into two types, \(n\ge r \text{a}\text{n}\text{d} \text{d}\text{a}\text{y}\text{s} \text{o}\text{f} n\le r-\)1. For 11 classifications of total 13 classifications, the median of the Be-7 concentrations of each station on days of \(n\ge r\) was greater than that on days of \(n\le r-1\) in more stations. For each of 7 classifications, it was significant \((p<0.05\)) by the binomial test.
(3) For each station, the inclination of the regression line of the daily Be-7 concentrations with respect to the numbers of daily earthquakes(M\(\ge\)5) in the world was calculated. In more stations (almost significantly (p=0.074) by the binomial test), each inclination was positive.
The Be-7 concentrations in the surface air in the world, as a whole, may increase on days when the daily number of earthquakes(M\(\ge\)5) in the world increase.