Every measurement has its units. For instance, weight is usually expressed in kilograms and pounds, heat in joules or BTU, and so on. Similarly, in order to compare the various earthquakes occurring in the world, a measuring unit has been devised based on the Richter scale.
In simple terms each occurring earthquake is measured by an instrument known as a seismograph, and the resulting spread of the earthquake waves is assigned a value based on its peak height on the graph. The scale grows by a factor of 10. That is, an earthquake measured 8.0 on the Richter scale is 10 times as powerful as a 7.0 earthquake; 100 times more than a 6.0 one; 1000 times more than a 5.0 one; and so on.
Why is it called "Richter" scale?
It is called Richter scale because it was developed by Charles Richter in 1935 at the California Institute of Technology. The scale was found convenient to use, and was therefore adopted universally.
Earthquakes and Tsunamis
Earthquakes and tsunamis have caused much damage to human life and property in history. In March 2011, a major 8.9-magnitude earthquake occurred in Japan, followed by a tsunami, which together have resulted in the worst catastrophe in over 100 years. To know how earthquakes can cause so much damage, it is important to understand their origin.
How earthquakes occur
Earthquakes occur when the rocks (or plates) lying under earth's surface push against each other and break. This can happen with the rocks lying under the landmass, or those under the seawater.This causes earthquakes, during which the rocks move against each other until they settle again. This process releases tremendous amounts of energy that causes the ground to shake violently. Any destruction that follows is a direct result of this.
Some important terms related to an earthquake:
- Plates: The underground rocks of earth's surface.
- Fault: Discontinuity along the rock's edge that causes damage to the plates.
- Focus: The point where the rock fault occurs.
- Epicenter: The point on the earth's surface directly above the focus.
- Magnitude: The measure of earthquake energy (expressed in terms of the Richter scale). A unit increase in magnitude corresponds to a ten-fold increase in the earthquake's destructive power.
Since earthquakes are natural phenomenon, these can't be avoided, let alone predicted. Certain parts of the world are earthquake-prone (like Japan), and hence the infrastructure there is usually designed to be quake-resistant. This, however, is no defense against the severe natural calamities.
When earthquakes occur in the ocean-beds, the released energy comes out through the water. This causes waves to be created on the water's surface, which move farther and farther away from the epicenter as they carry energy to the shores. Naturally, the more the magnitude of the earthquake, the higher the wave height will be. When these waves reach the land, they can cause destruction on any scale.
8.6 magnitude Earthquake on the coast of Indonesia and Tsunami Warning in Southeast Asia, should the world invest in building a mechanism to predict Earthquakes?