How and why do earthquakes occur?

An earthquake is caused by a sudden movement of rocks in the earth’s crust. Such movements usually occur along faults, which are thin zones of crushed rock separating blocks of crust.  

Earthquakes are usually caused when rocks underground suddenly breaks along a fault in the earth’s crust. When one block suddenly slips and moves relative to the other along a fault, the energy released creates vibrations called seismic waves that radiate up through the crust to the earth’s surface, causing the ground to shake. 

How do earthquakes form?

·         Earthquakes develop in the crust of the earth. The crust involves the earth’s surface, submarine levels, down to the ocean floors. The inner part of the earth contains massive energy. Some of this energy escapes through cracks and other volcanic activity, but the bulk of it is stored within the earth’s inner part, contained in the crust. 

·         The earth’s outer crust is held in place like a completed jigsaw puzzle, with rough edges and lines. The energy stored here causes the pieces to slide, glide, knock and move around each piece. These pieces best describe what we call ‘Tectonic plates.’ 

·         After a period of time, the built up energy and movement causes huge tension in the plates, and there is massive pressure on the fault lines. This intense pressure resulting from energy build up causes the fault lines give way, and plates move over, against or apart from each other. 

Thus, when two blocks of rock or two plates rub against each other, they don’t just slide smoothly; the rocks catch on each other.  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.


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