Bulgaria has been "very lucky" during the 5.9-magnitude earthquake that hit Sofia and other western regions early Tuesday morning, according to the head of a scientific team at the Bulgarian Academy of Sciences.

"We have localized the epicenter, and our scientists have discovered that there was only a partial movement of the fault so we all got very lucky," Professor Alexander Radulov, head of a team of geologists at the Geophysics Institute of the BAS told BNR Tuesday afternoon.

He explained that after visiting the site of the epicenter the researchers found that the fault had moved only 20-30 cm, and the earthquake can be characterized as "weak".

"However, none of that means that the other faults nearby cannot start moving," Radulov said.

He warned that aftershocks with a magnitude of up to 4 will likely be experienced for the next 4-5 days.

The earthquake that the Bulgarian capital Sofia experienced at 3 am on Tuesday has been the strongest in its history since 1858, i.e. in 154 years, historical records indicate.

On Tuesday, Bulgaria's territory saw over 60 weak aftershocks after the 5.8-5.9-magnitude it experienced early Tuesday morning, according to the Geophysics Institute of the Bulgarian Academy of Sciences.

All of the 60 aftershocks had magnitudes of over 1 on the Richter scale, and their epicenters were around the western Bulgarian city of Pernik, where the initial earthquake hit at about 2:58 am on Tuesday. Some of the major aftershocks had a magnitude of 4.2-4.7, and were felt in Pernik and Sofia.