An earthquake is when the Earth shakes, and it’s the vibrations what we feel. There are many causes of earthquakes: volcanic activity, meteorite impacts, undersea landslides, explosions of nuclear bombs, and much more, but the most common cause of an earthquake is sudden movement along faults. A fault is a crack in the Earth along which the rock of its two sides moves past each other (see diagram 1). “Pressure builds in near-surface rocks until the stress is so great that the rocks fracture and shift along a fault (55).” This, creates the shock waves that create an earthquake.

There are three laws about faults. The Law of Original Horizontality, the Law of Superposition, and the Law of Original Continuity. The Law of Original Horizontality states that sediments are originally

To locate the source of an earthquake is a huge task. You have to use the lengths of time the various seismic waves take to reach the seismograph, the locations if the epicenter and the hypocenter have to be determined. Another thing we must determine about earthquakes is the magnitude. The period is the length of time for a complete cycle to pass, and the amplitude is the height of the wave trace above its starting point (72). The period is inversely related to the frequency if the seismic waves. The period is equal to one divided by the frequency and is measured in hertz. To get an estimate of the size of an earthquake, we use the most common way called the Richter’s scale. Charles Richter created this scale in 1935 to describe the California earthquakes. This scale based its numbers off the bigger the earthquake, the greater the shaking of the Earth.

The study of seism waves generated by earthquakes is called seismology (seism means earthquake). In studying earthquakes there have been many instruments created to detect Earth motions such as the seismometers and to record Earth’s movements the seismographs. When the Earth moves, it releases energy in seismic waves that pass through the entire planet, which are known as body waves. The other waves that only move through the surface are known as surface waves. Now there are two main types of waves: primary and secondary. Primary waves or P wave is the fastest and is the first to reach a recording station. These waves are in a push pull motion. The secondary waves or S waves are then, the second to reach the recording station. These w

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