How Does An Earth Quake Start?

You can get a pretty good idea of what causes an earthquake from thinking about what happens during an earthquake. During an earthquake, there is a trembling of the ground. It is this trembling of the earth which may cause buildings to fall. So an earthquake is a trembling or vibration of the earth's surface. What makes it happen? Well, the rock of the earth's crust may have a "fault", a kind of break in the crust. The earth blocks shift. Sometimes the sides of the fault move up and down against each other. At other times, the sides of the fault shift lengthwise.

But when one rock mass has rubbed on another with great force and friction, we have a lot of energy being used. This vast energy that comes from the rubbing is changed to vibration in the rocks. The vibration is what we feel as an earthquake. And this vibration may travel thousands of miles.

The reason earthquakes take place in certain regions frequently and almost never in other regions, is that the faults in the earth's crust are located in these regions.