In April 1966, the gas radon in groundwater rise [3] In the year 1969, country Russia It was found that six months before the earthquake occurred. Electrical conductivity on groundwater change [4]
In April 1966 Radon gas in groundwater rising [3] In 1969, Russia. Found that six months prior to an earthquake. Conductivity changes in groundwater [4].
In April, 1998. 1966 radon in groundwater rise [3] in 1969 Russia found that six months before the earthquake. The electrical conductivity of groundwater changes 4 [].