- Giles: "It was an earthquake, Buffy. A not uncommon occurrence in Southern California. No reason to think it was anything more."
- Buffy: "Oh, I so have a reason. A darn good reason. The last time we had an earthquake, I died."
- — on an earthquake in Sunnydale.[src]
Earthquake was the shaking of the surface of the Earth, with often mystical causes and consequences, despite a natural occurrence in places like Southern California (including the cities of Sunnydale and Los Angeles). They had the tendency to either prevent an apocalypse, swallowing religious buildings whole or even imprisoning dangerous individuals; break an containment and freeing an individual; or act as portents, announcing prophecies or even apocalyptic commotions of the Hellmouth.
- 1812, Sunnydale. An earthquake caused a cave-in and swallowed the entire Sunnydale Mission building, trapping the Chumash vengeance spirit Hus.
- 1932, Sunnydale. An earthquake swallowed the Temple of Proserpexa, preventing the followers of Proserpexa to destroy all life on Earth.
- 1937, Sunnydale. An earthquake swallowed Order of Aurelius' church, entombing The Master.
- 1890s, Budapest. The Whirlwind enjoyed the chaos of a recent earthquake.
- 1997, Sunnydale. An earthquake announced the prophecy of Buffy's death and the Master's freedom.
- 1999, Sunnydale. An earthquake presages an apocalyptic attempt by demons to reopen the Hellmouth.
- 2002, Los Angeles. An earthquake announces the prophecy of Angel killing his own son.