On 29 December 2020, an earthquake of magnitude 6.2 on the Richter scale rocked near town Petrinja (Sisak-Moslavina county, Croatia), with an epicenter 5 km west-southwest of the town and at a depth of about 10 km. Before this event there were some foreshocks and aftershocks, the strongest were about 5 on the Richter scale. Officals announce that half of this town has been destroyed. The earthquake was felt throughout northern Croatia, as well as in many nearby countries.
Among other things, Marija Smolić (4th grade - Juraj Baraković High School Zadar) writes in her communication “Oil exploitation in Croatia: ... As already mentioned, Moslavina has a long tradition of oil exploitation. Although oil began to be extracted in 1854 by hand, until the beginning of the 20th century. there were no significant successes in oil production in Moslavina. There are 18 oil fields in the Sava Valley, but not all fields are operational. Stružec is the largest oil and gas field in Moslavina, but also one of the largest in Croatia. Along with Stružec, the most abundant fields in the Sava Valley are Žutica and Ivanić”. So, the oil and gas fields nearby to Petrinja were/are highly exploited. Stružec is only about 30 km from this town.
Reports say that the strongest earthquake near Petrinja was occurring at relatively shallow depth of about 10 km, followed by numerous intensive aftershocks at rather shallower depths (some of them even at a depth of about 1 km). In my opinion, increased and prolonged seismicity of the in the devastated region of Petrinja-Sisak-Moslavina is possible induced by oil/gas exploitation. This possibility is also indicated by the occurrence of numerous mud eruptions and huge holes in this area.