Earthquake

 
earthquake (also known as a quake, tremor, or temblor) is the result of a sudden release of energy in the Earth's crust that creates seismic waves. Earthquakes are recorded with a seismometer, also known as a seismograph. The moment magnitude (or the related and mostly obsolete Richter magnitude) of an earthquake is conventionally reported, with magnitude 3 or lower earthquakes being mostly imperceptible and magnitude 7 causing serious damage over large areas. Intensity of shaking is measured on the modified Mercalli scale.

At the Earth's surface, earthquakes manifest themselves by shaking and sometimes displacing the ground. When a large earthquake epicenter is located offshore, the seabed sometimes suffers sufficient displacement to cause a tsunami. The shaking in earthquakes can also trigger landslides and occasionally volcanic activity.

Why Do Earthquakes Happen?

Earthquakes are usually caused when rock underground suddenly breaks along a fault. This sudden release of energy causes the seismic waves that make the ground shake. When two blocks of rock or two plates are rubbing against each other, they stick a little. They don't just slide smoothly; the rocks catch on each other. The rocks are still pushing against each other, but not moving. After a while, the rocks break because of all the pressure that's built up. When the rocks break, the earthquake occurs. During the earthquake and afterward, the plates or blocks of rock start moving, and they continue to move until they get stuck again. The spot underground where the rock breaks is called the focus of the earthquake. The place right above the focus (on top of the ground) is called the epicenter of the earthquake.

Try this little experiment:

Break a block of foam rubber in half. Put the pieces on a smooth table. Put the rough edges of the foam rubber pieces together. While pushing the two pieces together lightly, push one piece away from you along the table top while pulling the other piece toward you. See how they stick? Keep pushing and pulling smoothly. Soon a little bit of foam rubber along the crack (the fault) will break and the two pieces will suddenly slip past each other. That sudden breaking of the foam rubber is the earthquake. That's just what happens along a strike-slip fault.

earthquakes occurred naturally

Tectonic earthquakes will occur anywhere within the earth where there is sufficient stored elastic strain energy to drive fracture propagation along a fault plane. In the case of transform or convergent type plate boundaries, which form the largest fault surfaces on earth, they will move past each other smoothly and aseismically only if there are no irregularities or asperities along the boundary that increase the frictional resistance. Most boundaries do have such asperities and this leads to a form of stick-slip behaviour.

In my opinion, we can not avoid earthquake  but we can prevent earthquake damage. The first we must move out the hazard area, and develop technology to predict disaster, then we can prepare solution to prevent it. For example we can move people to safe area or prepare remedy ,food and water. We must develop technology to predict and detect earthquake as soon as possible so that we can decrease extremely damage  from earthquake.

Referencing

www.wikipedia.org

Hayes,L (1999) vocalno and earthquake ,Author : Susanna van Rose Published by DK Publishing

Earthquake Protection by Coburn, Andrew/ Spence, Robin J. S. John Wiley & Sons Inc Revaluation Books, Exeter, DEV, United Kingdom