why do some earthquakes occur away from the faults on the map?

Question

I've seen the earthquake map of California and found out some earthquakes do not occur on the fault lines. Why do some earthquakes aapear to be located away from the faults on the map?

Answer 1

You've got to remember that the fault lines are only fissures, or cracks in the earth's crust, where seismic pressure has caused the crack during past quakes. They are not necessarily located directly above the source of the seismic activity. That action starts deep in the earth at many different locations, and the pressure waves just travel up toward the surface along the path of least resistance. It's like if you had cracks in the walls and floor of your house from past quakes: another quake could come along that originated from a different location, and create new cracks. The damage wouldn;t always be limited to the same fissures.

Answer 2

A fault is a movement of earth. Some fault lines are major, but there are many minor fault lines. There might be dangerous undiscovered faults in California. When there is an avalanche on a mountain, where the split was was the fault line. The creation of artifical lakes have been known to cause so much land shifting that earthquakes were created.