Actually, it wasn’t so much the 1906 earthquake that destroyed the city of SF so much as the firestorm afterward - a firestorm made all the worse because the corruption of the politicians of that time refused to listen to the fire chief’s requests for an independent water supply for fighting fires. The quake broke water mains and cut off water for fighting fires to most of the city.
The water mains in San Francisco are still vunerable to breaking today from a major quake. The other reason most of the city was destroyed is because of landfill.