San An ‧ dre ‧ as fault, the /ˌsæn ændreɪəs ˈfɔːlt/ BrE AmE
a crack in the Earth’s surface which runs from the north to the south of California in the western US. The large areas of rock on either side of this crack are slowly moving in different directions, and this sometimes causes ↑ earthquake s (=when the Earth’s surface suddenly shakes, causing a lot of damage) . ⇨ ↑ San Francisco , ↑ plate tectonics