Earthquakes

An earthquake is a natural disaster that can have incredibly destructive results on the earths crust and endanger many living organisms that dwell on that crust. An earthquake occurs when massive amounts of stored energy are released from the earth. This release of energy can be caused by the slipping of tectonic plates or sometimes even be influenced by humans.

Earth is a stratified planet. This means that it is made up of multiple layers. The inner layer is a ball of molten rock that rotates within the earth. There are many layers that are on top of this pliable ball of molten rock. The outer layer is called the crust. Earth's crust is very thin when compared to the other stratified layers of the earth. It would be like comparing the skin of an apple to the interior of the apple. The crust and other layers "float" upon this mantle core. The crust of the earth is made up of multiple pieces. Each of these giant pieces is called a tectonic plate. Earthquakes are commonly found in areas where these plates rub together.

When an earthquake occurs is creates seismic waves. These seismic waves are much like sound waves and can cause the destruction of many objects due the vibrations it can cause. The most common type of seismic waves that occur in an earthquake are S and P waves. S waves are shear waves, which means that the ground is displaced perpendicularly to the direction of propagation. P waves or compressional waves, which means that the ground is alternately compressed and dilated in the direction of propagation. S waves are much more destructive because they travel at a lower wavelength which means they have a larger amplitude. This increase in amplitude is destructive to things such as buildings because they cannot handle the type of vibrations is may cause.

The Richter scale is a mathematical logarithm that is used to determine the strength of an earthquake. Since it is an exponential function the strength of an earthquake increases exponentially for ever increase in the scale. The richter scale is not an extremely accurate method for measuring the power of an earthquake because earthquakes can occur at different depths and strike in different areas of the world.

Believe it or not but there are over 8,000 earthquakes ever day on our planet. They are just too weak to be detected without special equipment. The amount of earthquakes that are actually felt each year is around 49,000.