ABOUT EARTHQUAKES

An earthquake is a natural phenomenon like rain. Earthquakes have occurred for billions of years. Descriptions as old as recorded history show the significant effects they have had on people’s lives.

Definition of an earthquake

In simple terms, an earthquake is caused by the constant motion of the earth’s surface. The earth’s rock layer is broken into large pieces. These pieces are in slow but constant motion. They may slide by each other smoothly and almost imperceptibly.

From time to time, the pieces may lock together and energy that accumulates between the pieces may be suddenly released. The energy that is released travels through the Earth in the form of waves. People on the surface of the earth then experience an earthquake.

Earthquakes are the sudden, rapid release of energy stored in rocks.

EARTHQUAKE EPICENTRES

The epicentre of an earthquake is the place on the Earth’s surface directly above the focus or (hypocentre), the place inside the earth where the quake originates. Earthquake foci are usually somewhere between the surface and 100 km in depth. In some areas, however, the foci may be as deep as 700 km.

Maps of earthquake epicenters show that most earthquakes have occurred in certain well-defined regions of the Earth. Because these regions tend to be relatively long and narrow they are sometimes referred to as earthquake belts.

One large belt of epicentres run through the Mediterranean Sea, Asia Minor, and the Himalayan Mountains and into the eastern Indian Ocean. A second large belt runs northwards though the western Pacific Ocean, the Japanese Islands, the Aleutian islands and the west coasts of North and South America. The longest belt of earthquake epicentres runs through the central regions of most ocean basins.