by Christopher Anderson

Created on: September 01, 2011   Last Updated: September 20, 2011

What is an earthquake? An earthquake is what happens when two large land masses pass over one another. On the surface where the quake is most visible is called a fault or fault plane. Below the surface, the point at which the earthquake starts is called the hypocenter, and on the surface it is know as the epicenter.

Occasionally a seismic event like an earthquake has what is known as foreshocks, Yes the opposite of aftershocks. Foreshocks are much smaller earthquakes are smaller quake that come before the main quake. There is no way to ascertain if a foreshock is the main quake until the main quake occurs. The larger quake is called the mainshock, which is always followed by an aftershock. Much smaller quakes can follow in the same position as the main quake. Aftershock can surprisingly follow for weeks, months, and even years after the mainshock.

What are the causes of an earthquake and where are they most likely to happen? The earth consist of four major layers, the inner core, outer core, mantle, and the crust. The earths crust and the top of the mantle both comprise a thin layer on the surface of the planet. This thin layer of earth is make many piece of earth called plates, they are known as tectonic plates. Think of them as large puzzle pieces. Most of the earthquakes around the globe happen on these faults. The edges of the plates are rough and in motion, they tend to get caught on one another and continue to move. After some time, the snags give way with such a force and you have an earthquake.

The earth tends to move when there is a quake, because while the plates are stuck together, the rest of the plates continue to move. The plates that are stuck together store up energy, when the plates can no longer stay stuck together the force of the stored energy is released. The energy spreads out in every direction. The seismic event is like a wave across the earth, upon reaching the surface the ground shakes terribly.

Scientist record earthquakes with a device know as a seismograph. Making a recording called a seismogram. The device sits fast on the ground, with a heavy weight descended from a piece of string or wire. The weight on the string absorbs the movement. A seismograph measures the variations between the moving parts of the seismograph and the fixed part of the device are what are measured.

Earthquakes are large tectonic plates that slide over one another, the energy stored from this movement is what causes the earth to shake. There are faults all over the globe, most quakes occur along these faults. The earth does not consist of a solid piece of rock, these plates move and when they get hung up on another land mass, they result is earthquakes. With the help of scientist and the seismograph, we are at a better understanding of earthquakes but a long way away from predicting them.

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