Earthquake is a Normal Spell Card.
Spell Cards are usually activated from the hand on your turn unless their type gives another timing window.
On the current TCG and OCG Forbidden & Limited lists tracked here, Earthquake is Unlimited.
YGOPRODeck lists Earthquake for these formats: GOAT, OCG GOAT, Duel Links, Speed Duel, Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of Earthquake appears in Ancient Sanctuary (AST-043) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Earthquake is about $0.03 on Cardmarket (prices change frequently).
