As global citizens its our responsibility at Individual, Collective, Government or Corporate level to help "Save Earth" before its too late

 
  Home Earth Earth News Act now Green Techs  Pictures  Videos  Go to Blog

Earthquakes

Science Behind Earthquakes

Dr. Abhinandan Bhardwaj PhD

 

Earthquake

The term "earthquake" is used to describe any seismic event which generates seismic waves. An earthquake occurs as a result of a sudden release of energy in the Earth's crust which creates seismic waves. They occur along faults (fault is a  planar breaks in rock along which there is displacement of one side relative to the other). An earthquake is what happens when two blocks of the earth suddenly slip past one another.  The surface where they slip is called the fault or fault plane.

 

How Are Earthquakes Measured?

The magnitude of earthquakes is measured using Richter's Scale.

 

How Often Earthquakes happen?

Every day our Earth experiences earthquakes in different parts of the world. More than a million earthquakes occurs all around the world each year but most of them are too small to cause any damage and are barely felt by humans.  Earthquakes with magnitude of about 2.0 or less are usually called microearthquakes. They are generally recorded only on local seismographs.

 

Focus and Epicenter:

The point on a fault at which the first movement or break occurs during an earthquake is called Earthquake's Focus. The point directly above the focus on the surface of Earth is called epicenter. Major earthquakes dramatically demonstrates that Earth is a dynamic, ever changing system.

 

Seismic Waves:

When an earthquake occurs it releases its stored up energy in the form of three types of waves. These waves are called seismic waves. There are three main types of seismic waves - P S and L. P and S waves travel through the interior of the Earth. P are compressional waves.  P waves are also called Primary waves and they  travels through earth as sound waves travel through the air. S waves are also called Secondary waves or  shear waves, involving side to side motion of molecules. L waves are called longitudinal waves are the slowest as they travel from Earth's surface, they cause the maximum structural damage.

 

Causes of Earthquake:

Crust of the Earth  is constantly moving. This sections of the crust are called plates and the process which moves these plates is described in more detail in Plate tectonics page. To learn more about Plate tectonics click here.

These plates constantly pushing against each other due to forces produced by its semi viscous interior. The areas where these plates collide often have increased volcanic and earthquake activity.

 
There are about 20 plates along the surface of the earth that move continuously and slowly past each other. When the plates gets crushed or stretched, huge rocks form at their edges and the rocks shift with great force, releasing tremendous amount of energy which in turn causes an earthquake.

Watch Video Plate Tectonics

 

Other causes of Earthquakes are Volcanic activity, Underground nuclear explosions , landslides etc. About 80 percent of all the Earth's earthquakes occur along the rim of the Pacific Ocean. This is also called as the "Ring of Fire" because of extreme volcanic activity there. Most earthquakes takes place at fault zones, where tectonic plates collide or slide against each other.

 

Earth's Plates ( Photo Source: Nasa)

In a sequence of earthquakes there is normally one event significantly larger than the other which is called the first shock or main shock, any earthquakes after that are called aftershocks.

How do earthquakes cause damage?
Structural damage  in an earthquake is caused by the ground shaking. The amount of ground shaking that might be produced depends on magnitude or energy released in an earthquake, distance from the focus or source, focal depth, type of faulting, and type of material are important factors.
In general, large earthquakes produce ground motions with large amplitudes and long durations. Large earthquakes also produce strong shaking over much larger areas than do smaller earthquakes. In addition, the amplitude of ground motion decreases with increasing distance from the focus of an earthquake. The frequency content of the shaking also changes with distance. The frequency of ground motion is an important factor in determining the severity of the damage to structures.

Can Earthquakes be predicted?

The answer to this question is no. Until now we do not have any concrete technology which can predict exact timing and place of any earthquake.

What should be done to avoid Earthquake ?

Nothing much can be done to avoid earthquakes as earthquakes happen all the time everywhere on Earth. However most severe earthquakes occur along the major fault lines and plate boundaries around the world. If possible do not live in the areas which fall within these boundaries or fault lines. But if you happen to live around these places then try to build the home which are earth quake proof. For more info and tips... click here

 

Watch Video of actual earthquake happening

 


 

 MAJOR  CONCERNS

 

Learn More
Richter's Scale
Scale used to measure Earthquakes. Learn about what is Richter Scale and who Charles Francis Richter was.

Dr. Abhinandan Bhardwaj PhD

 
Mercalli's Scale
Another scale used to measure Earthquakes. Learn about  who Giuseppe Mercalli was.

Dr. Abhinandan Bhardwaj PhD

 
Plate Tectonics
Learn about How earth's Plates move, how they form and how they get destroyed.

Dr. Abhinandan Bhardwaj PhD

 
Earthquakes Tips
Learn about what needs to be done when an earthquake strikes, or if you happen to live in an earthquake prone area.

Dr. Abhinandan Bhardwaj PhD

 
Tsunamis
Learn about Tsunamis and  how under sea earthquakes can lead to tsunami formation.

Dr. Abhinandan Bhardwaj PhD

Useful links
Daily Earthquake Watch
Earthquakes happens everyday. See where Earthquake happened daily, weekly.

USGS

 
Sponsored Links
 
 
 
 
 

 

 
 
  Our Mission Contact Us

About Us

 Copyright 2008  -  "Save Earth international" A Non Profit Organization, all rights reserved. Privacy Policy