Joel Achenbach has a good posting about the 1906 San Francisco earthquake that includes this:
In that day and age, no one knew basic structure of the surface of the Earth — how it is divided into plates that move, grind against one another, build stress. People didn’t know that continents could migrate across the globe. They had no grasp of tectonic forces that shaped the dramatic landscape of California. They didn’t know anything of mid-oceanic ridges and subduction zones and the relationship between subducting crustal plates and volcanoes. They didn’t even know if faults in the Earth caused earthquakes, or if it was the other way around. You know, the ground shakes, maybe that causes those cracks and scarps?