Earthquakes
Introduction
An earthquake commonly known a tremor results from sudden releases of massive energies in the Earth’s crust creating massive seismic waves. They are measured using observations made from seismometers for magnitudes of approximately 5 and higher with the smaller magnitudes mostly being measured on the Richter scale (Kusky 45). Earthquakes of magnitudes 3 and lower are weak and mostly imperceptible those of magnitudes 7 and above being potentially seriously dangerous depending on their depth causing damages in large areas. Even though there isn’t any limit to magnitudes that earthquakes may reach, the highest magnitude that has ever been recorded has been of slightly above 9.
Background
On the surface of the Earth, earthquakes are experienced as shaking and in other cases, ground displacement in which cases sometimes cause volcanoes and at times tsunamis when the ground displacement happens offshore. Generally, the word earthquake describes any seismic event that is either caused by humans or natural and generates seismic waves. They are mostly caused by the rupture of Earth’s geological HYPERLINK “http://en.wikipedia.org/wiki/Fault_%28geology%29” o “Fault (geology)” faults, and also by other natural and manmade events such as mine blasts, landslides, HYPERLINK “http://en.wikipedia.org/wiki/Underground_nuclear_testing” o “Underground nuclear testing” nuclear tests, and volcanic activity. The point of an earthquake’s initial rupture is known as its HYPERLINK “http://en.wikipedia.org/wiki/Hypocenter” o “Hypocenter” hypocenter or HYPERLINK “http://en.wikipedia.org/wiki/Focus_%28earthquake%29” o “Focus (earthquake)” focus. The point at the ground level that is directly above the earthquake’s hypocenter is known as the HYPERLINK “http://en.wikipedia.org/wiki/Epicenter” o “Epicenter” epicenter.
Types of earthquakes
There are generally four types of earthquakes. These are volcanic, Tectonic, explosion, and collapse. Volcanic earthquakes are those earthquakes that are a resultant of massive tectonic forces that occur when volcanic activity as a result of movement if magma occurs or are experienced. These types of earthquakes also serve as early warning of volcanic eruptions. After the earthquakes that are experienced, volcanoes erupt within several miles of where the tremors were felt depending on the pressure levels in the mountain.
Appendix: 1
Tectonic earthquakes are those earthquakes that occur in the events that the Earth’s crust breaks owing to great geological forces that build on rocks and the adjoining plates causing chemical and physical changes. These are the most common type of earthquakes by far owing to the various global forces that exist (Prokos 59). They begin by initial rapture at points along the surface of the fault by a process called nucleation. There has been evidence to support the notion that there is usually some kind of preparation involved with the most evidence coming from foreshocks that precede almost 40% of earthquakes. They generally occur at points of the earth where there are sufficient strain energies enough to drive various fracture propagation along the fault plane.
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Collapse earthquakes are those small earthquakes in underground mines and caverns caused by various seismic waves that are produced from explosions of surface rocks. They mainly occur on the mining fields where explosives are necessarily used to loosen rocks. Many miners have been known to lose their lives inside mines to this type of earthquake. These types of earthquakes are caused by landslides as well.
Explosion earthquakes are earthquakes that occur as a result of the detonations of chemical and/or a nuclear device. When these devices are detonated below ground level in boreholes, there is a massive release of nuclear energy, vaporizing surrounding rocks consequently creating a huge spherical cavity. There have been various nuclear explosions recorded, mainly test blasts with massive earthquakes, of up to 4.3 magnitude earthquakes being recorded on the Richter scale.
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Major earthquakes around the world that have been recorded include one that occurred in the Chinese province of Shaanxi on 23rd January 1556 that killed over 830,000 people with most of the population at the times living near and inside artificial caves inside cliffs. In the year 1976, an earthquake occurred in Tangshan in China killing about 650,000 people making it, by death toll, the largest earthquake in the 20th century. By seismograph, the largest measured earthquake measured a magnitude of 9.5 occurred in Chile in 1960. In recent times the Japanese earthquake of 2012 measured a staggering 9.0 magnitude on the Richter scale (Walker 85).
Conclusion
Earthquakes are naturally occurring activities in the earth’s crust caused by various factors explained above. The prediction of this phenomenon has come a long way in recent times aided by the advancement in technology. Previous civilizations mostly used to use animal behavioral characteristics to try predict earthquakes. Animals the world over including in recent times have been known to exhibit unusual behaviors with research showing that they have instinctive nature that warns them in advance. Very few humans have been known to instinctively sense earthquakes probably due to the erosion of these senses in the evolutionary process. The human society has come a long way in adapting to areas that are prone to earthquakes that include the ring of fire. Early warning systems have been adopted and various building techniques that are less prone to collapsing during earthquakes have been developed in the hopes of saving lives in the event of an earthquake. With advancing technology, the advancement of human technology will greatly help in the prediction and subsequent saving of human lives since the continuous movement of the earth’s tectonic plates will definitely continue.
Works Cited
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Kusky, Timothy M. Earthquakes: Plate Tectonics and Earthquake Hazards. New York: Facts
On File, 2008. Print.
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Prokos, Anna. Earthquakes. Pleasantville, NY: Gareth Stevens Pub, 2009. Print.
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Walker, Sally M. Earthquakes. Minneapolis, MN: Lerner Publications, 2008. Print.
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Appendix: 1
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Appendix: 2
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Appendix: 3
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