The elimination rate of radon gas from soil depends on the rate of uranium content of the selected region, so how did the last earthquake in midlist regions affect the emanation rate of radon gas?
The concentration of Radon in the air of the soil depends on the porosity, permeability, gas carrier and water content too.
So, before and during an earthquake event, the "deformation" of the all geomorphological level. High, low levels of soil and bedrock. The changing of it can change the micro and macro structures: now you have a "big" Radon availability.