This type of boundary is called a transform fault, where the Pacific and North American plates horizontally grind past one another without creating or destroying crust.

Because the Pacific and North American plates slide horizontally rather than pulling apart, there is no geologic mechanism for the land to physically fall into the sea.

Los Angeles sits on the Pacific Plate, which creeps northward at about two inches per year, meaning it will eventually sit adjacent to San Francisco in 15 million years.

Wallace Creek in California famously demonstrates this horizontal shift, as its water flow takes a sharp, right-angled jog exactly where it crosses the active fault line.