Spain's National Geographic Institute said the earthquake at 0532 local time measured 4.2 magnitude, the strongest yet in the region around the Gulf of Valencia, a zone not normally known for seismic activity.
The government last week ordered a stop to injections of gas into the European Investment Bank-backed Castor storage plant, while scientists study whether the injections triggered the quakes.
Industry Minister Jose Manuel Soria said on Tuesday there was no confirmed link between the earthquakes and the work on the plant, but seismologists have said they believe there is a connection, because the tremors started at the same time as the injections of gas.