The earthquake can be felt as a slight tremor or it can be a violent shaking that causes a lot of damage.The Earth’s internal forces some time cause the continental plates to move. The movement may result in sudden shifting or breaking of rocks along a fault line. This movement releases a great energy in the form of shock waves. The point of origin is called the focus.The shock waves move out in concentric circles very similar to the ones that are created when a pebble is dropped in a pond. At times, such waves are strong enough to reach the surface of the Earth.The point on the Earth’s surface immediately above the focus, is called the epicenter. From this point, the waves move outward decreasing in strength as they move away. The greatest impact being felt at the epicenter, this region suffers the greatest damage.The shock waves, also called seismic waves, are measured by an instrument called seismograph. The severity of the earthquake is measured on a Richter Scale. It measures the intensity of the earthquake on a 0-9 scale. A figure of 2 or less is barely felt while a figure above 6 means a major earthquake.Young fold mountain regions are earthquake-prone regions. Though seismologists around the world are trying to find new methods of predicting earthquakes, they have met with limited success. The foothills of the Himalayas are an earthquake-prone area because this is the region where two continental plates meet.