Zhen, Thunder refers most of all to an earthquake, but also to thunder or a lightning strike. The trigram brings new ideas or beginnings, impulses and intuition, a breakthrough, sudden changes, a wake-up call. Thunder inside can give you green fingers, a connection with nature's demands, the wish and the power to start at the core and to rejuvenate, because Thunder gives respect for what is true and essential.
When Thunder is above or outside, the lower trigram expresses itself in accord with the properties of Thunder. Or your surroundings demand it. Actions can be rash and unrestrained. Things happen suddenly and can have radical consequences. Or things happen wich look frightening but don’t do any damage. This can be a time when things finally start to happen, when new ideas suddenly sprout, or when deeper values or knowledge enter consciousness.
When Thunder outside is out of balance, actions are rash and destroying, ideas have no structure but depend on wild guesses, revolutions are destroying instead of opening up new possibilities.
Other translations: shake, emotional, invigorate and rejuvenate, power, majesty, respectful, frightened.