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Thecrust of the earth comprises of giant pieces of rocks called plates.They are always in a continuous motion, and when they collide, theyproduce a lot of energy. The shaking of earthquakes is caused by themovement of tectonic plates along fault lines. The fault lines existat the borders of these plates (Sepahban, 2014). A seismic activityoften consists of other multiple smaller quakes. At times there areminor vibrations or foreshocks that take place before the occurrenceof the main shock. The largest quiver is called the mainshock, and itcauses a lot of damage. Mainshocks are often followed by smallershudders known as aftershocks (Sepahban, 2014). The aftershocks arefelt days after the occurrence of the mainshock. This paper willdiscuss what an earthquake is, what their causes are and how they aremeasured.

Thetectonic plates are always in a slow but continuous motion, formingnew crusts that grind old boulders into smaller particles and dust.When these plates move, the stones beneath the earth surface arepulled and pushed. Their movement can create immense pressure, whichwhen released, it causes an earthquake. Most of these movements areconsistently slow, but when a sudden change occurs, a mainshock canarise. The vibration of an earthquake spread out from the focus, theplace where the rocks slipped or broke, in a sequence of waves. Thefirst type of wave is the primary force that pushes and pulls therocks (Hamilton, 2012). They are the least harmful of all theearthquake waves. The next type is the secondary waves that make therocks move up and down in a ripple. They cause more damage than theprimary waves. They also result in much damage away from theepicenter – the point on the earth surface where beneath it theearthquake originated.

Mostearthquakes occur due to natural forces, but some are triggered byhuman activities. Actions such as mining and nuclear testing can leadto seismic activity. Most tremors associated with human activitiesare not as catastrophic as those that happen naturally (Smith, 2012).The blasts from weapons of mass destruction and the events thathappen in the mining fields cause interference with the movements ofthe tectonic plates. cannot be prevented however, somemeasures can be taken to ensure that when they take place, they donot harm or kill people or even destroy property. Scientists havecome up with a way of predicting and measuring the intensity of anearthquake when it happens. They use a machine known as theseismograph to measure the ground’s movements (Smith, 2015).Charles Richter invented the machine in 1935 (Hamilton, 2012). TheRichter Magnitude Scale is used to assess quakes. Scientists make useof the information from the seismograph to give a seismic activity ascale number. If the number is high, then it signifies that the quakewas strong (Hamilton, 2012).The Richter Scale starts from zero to 10.The destructive and catastrophic earthquakes measure from five andabove. The most powerful earthquake that has ever been recorded wasone that occurred in Chile, South America, in the year 1960 it had amagnitude of 9.5.

Inconclusion, earthquakes could take place during the day or at night.It could also happen on the land or underwater. The earthquake thatoccurred in the Indian Ocean and caused a tsunami is a perfectexample of a tremor that happened underwater. Natural forces causemost quakes, but there are others that can originate from humanactivities. Such actions include nuclear testing and mining. Finally,a seismograph is used to measure seismic activities. It has a Richterscale of zero to 10. Quakes that measure above five on the Richterscale are the most harmful and may cost many lives.


Hamilton,S. L. (2012). . Minneapolis:ABDO

Sepahban,L. (2014). Thescience of an earthquake. Ann Arbor: Cherry Lake Publishing

Smith,E. (2015, April 28) How earthquakes are mearsured? CableNews Network. Retrievedfrom