In real life, the San Andreas Fault is a large continental fault from San Francisco to Bombay Beach, California, and it marks the boundary between two tectonic plates.
The San Andreas Fault Line can be seen in GTA San Andreas as an underwater ridge, located in the San Fierro Bay. The crack starts just north of Jizzy's Pleasure Domes in San Fierro, and it runs along the seabed and comes to an end at a wall of sandstone that goes back up towards the land. The crack is with no doubt based on the real-life San Andreas Fault in California (on which San Andreas is based on), which is also presumably what the State of San Andreas is named after. This is most likely the reason why the Fault Line is in the game. It most likely contributed to the San Andreas Earthquake.
- There is a 2015 movie called San Andreas that features a disaster scenario about this fault line, although it is not GTA San Andreas related, because game was released 11 years before the movie.
- There are Sharks spawn points in the area, which can be seen in DarkMythHunter's investigation.
- The host of Radio Bounce, the Funktipus, can be heard referencing the San Andreas Fault by claiming that the SA fault is not his fault in-game.