“Looking at a map, check the Salton Sea’s location and continue that south into the Gulf of California in Mexico. It appears to be a natural breaking point, right where the Colorado River dumps into the Gulf.”
Yep... That was once all part of the sea of Cortez, the geology points towards Baja once being an island with a strait at Palm Springs west through to San Bernardino. The Pacific plate has since pushed it up through subduction and is still pushing it up. That is a major crust movement zone right along through there as you say.
Yeah - It’s splitting like the narrow Seas around the Great Rift valley now in Ethiopia and the Gulf of Aden, Red Sea : The Salton Sea area is below sea level. It “should be” naturally flooded by the Colorado River if dams and dikes had not been built - and then repaired several times! - between the 1870’s and the final Hoover Dam improvements and canals in the 1930’s.
Baja California is a long, narrow split-off piece of land moving north-northwest towards San Francisco that is divided from the rest of Mexico by these fault lines through the Salton Sea and Imperial Valley.