Petrashevski Circle is an event for 
Russia. It can happen at anytime between 1849 and 1852 if Russia is at peace. The author Mikhail Petrashevski is exiled to Siberia and the literary circle around him, which included people like Fyodor Dostoyevski, is outlawed.
It has a mean time to happen of 5 months, which is decreased by 25% af 1850 and another 5% after 1851.
It removes 2 plurality from Russia. On the other hand, it removes 1 consciousness from all 
capitalists, 
aristocrats and 
bureaucrats in the entire country.
The ingame text reads:
Founded in 1844, the Petrashevski Circle discussed political reforms in Czarist Russia. Among the Circles members were people like Fyodor M. Dostoyevski. In 1849 123 members of the circle were arrested, and Petroshevski himself was sent to Siberia.
Unlike what would be logical from the describtion, the event can happen regardless of Government form and the event description will not change.