"The windows shook as if a train was flying overhead or a very long train was passing by," the 55-year-old told news agency AFP by telephone.
"The fact is that in the area of the fault line there exists accumulated energy that, pushed by the gas injections, ends up being released," he added.
"It is very unlikely that there will be earthquakes of a stronger magnitude," Suarez said.
Three other underground gas storage plants exists in Spain — in Huesca at the foot of the Pyrenees Mountains, in Guadalajara in central Spain, and in Bermeo in the Basque Country.
No seismic activity has been recorded near those plants.