By Nayyar Alam Zaigham You may have experienced an earthquake. Cups and plates on the table rattle, furniture on the floor moves all by itself, hanging lamps and ceiling fans sway to and fro and the floor under your feet appears to be swinging.
Earthquakes occur because of a sudden release of stored energy.
This energy has built up over long periods of time as a result of tectonic forces within the earth. Most earthquakes take place along faults in the upper 25 miles of the earth's surface when one side rapidly moves relative to the other side of the fault. It is these seismic waves that can produce ground motion which people call an earthquake. Each year there are thousands of earthquakes that can be felt by people and over one million that are strong enough to be recorded by instruments. Strong seismic waves can cause great local damage and they can travel large distances.