why do earthquakes occur?

Answer 1

An earthquake is a phenomenon that results from and is powered by the sudden release of stored energy in the crust that propagates seismic waves. At the Earth's surface, earthquakes may manifest themselves by a shaking or displacement of the ground and sometimes tsunamis, which may lead to loss of life and destruction of property.

Earthquakes may occur naturally or as a result of human activities. In its most generic sense, the word earthquake is used to describe any seismic event—whether a natural phenomenon or an event caused by humans—that generates seismic waves.

Types of earthquakes Naturally occurring earthquakes Most naturally occurring earthquakes are related to the tectonic nature of the Earth. Such earthquakes are called tectonic earthquakes. The Earth's lithosphere is a patchwork of plates in slow but constant motion caused by the heat in the Earth's mantle and core. Plate boundaries grind past each other, creating frictional stress. When the frictional stress exceeds a critical value, called local strength, a sudden failure occurs. The boundary of tectonic plates along which failure occurs is called the fault plane. When the failure at the fault plane results in a violent displacement of the Earth's crust, the elastic strain energy is released and seismic waves are radiated, thus causing an earthquake. This processes of strain, stress, and failure is referred to as the Elastic-rebound theory. It is estimated that only 10 percent or less of an earthquake's total energy is radiated as seismic energy. Most of the earthquake's energy is used to power the earthquake fracture growth and is converted into heat. Therefore, earthquakes lower the Earth's available potential energy, though these losses are negligible Earthquakes occurring at boundaries of tectonic plates are called interplate earthquakes, while the less frequent events that occur in the interior of the lithospheric plates are called intraplate earthquakes.

You could get more information from the link below...

Answer 2

Earthquakes occur due to internal Earth pressures moving the tectonic plates that form the Earths crust.

Answer 3

The surface of the earth is made of a number of plates.
These slide about and when one grinds against another you get an earth quake.
If they grind on top of each other the boiling magma underneath gets through and comes to the surface as a volcano.
I know this is a simplistic answer. If you want full details, search the Internet, there is lots to be read on the subject.

I have seen your answer elsewhere on the subject of enzymes about which I know nothing and you seem very knowledgeable. Can't believe you don't know about earthquakes!!

Answer 4

Take a digestive biscuit, break it in half, shake off the crumbs, place the two halves on a table with the broken edges back together, now try and slide the two halves past each other, this would be like two plates on earth trying to slide against each other. The break, where your biscuit halves join each other, can be considered as a fault line, and as you increase the load on this fault line it will give way. Earthquake. :o)

Answer 5

Earth quakes are caused when two area of the earth move against each other:
The best one I can think of is the continents of Africa is slowly moving North towards Europe, and Asia is moving west and as they push against the continent of Europe the land vibrates & these vibrations are the earth quakes. So that is why Italy, Turkey, Greece and a few other countries have earthquakes.

Answer 6

Tectonic Plates moving.

Answer 7

the earth has several plates and when these plates collide an earthquake occurs.

Answer 8

http://www.seismo.unr.edu/ftp/pub/louie/class/100/plate-tectonics.html

Plate Tectonics, which are located under the surface of our land and sea bottoms, shift and slide against eachother, causing earthquakes. Try the site above, it is very informational. God Bless =]

Answer 9

the continents and oceans as we know it are on big plates. The plates are floating on the mantle, and the mantle has it's own movement. When this movement is altered or centered, the plates shift suddenly and sometimes violently.

Answer 10

because sometimes one of the 4 elephants that carries the earth on its back slips on the shell of the great a'tuin