Introduction
Earthquake is the shaking of the surface of the earth that results from the sudden release of energy from the lithosphere of the earth thus creating seismic waves. Earthquakes usually range from the weak tremors that are not felt by people to serious and violent ones that are which can destroy properties and loss of lives. Earthquakes take place by shaking and displacing the ground. When the epicenter of the earth is located at the offshore, it can get entirely displaced thus leading to severe earthquakes known as a tsunami ( Lomnitz, 2013 ). In other words, an earthquake is mainly used to describe a seismic event which can either be human-made or natural and that which results to the generation of the seismic waves. The initial rapture of the earthquake is mainly known as hypocenter, and the point directly above the hypocenter is known as the epicenter. The tectonic earthquakes usually take place as long as there is enough elastic energy that is capable of causing a fracture along the fault plane.
Causes of Earthquakes
Earthquakes are mainly caused by the movement of tectonic plates within the earth crust. When the tectonic plates ride over one another, an orogeny is caused, and this can lead to a severe earthquake. The plates are usually in continuous slow motion. The boundaries between the moving plates form large faults on the surface of the earth. When these faults come in contact, stress is caused, and this leads to a sudden breaking and release of the stored energy in the form of shock waves ( Cui, Huang & Pei, 2016 ). This sudden release of energy causes the surface of the earth to tremble in what is referred to an earthquake. The sudden movement of the tectonic plates on the surface of the earth is, therefore, the primary cause of the earthquake. As these plates collide, a lot of stress is produced which then result to the sudden release of too much energy capable of shaking the surface of the earth. Volcanic eruptions can also cause earthquakes to take place. This is mainly in the volcanic areas where the release of the volcanic materials is accompanied by a high-pressure magma leading to the shaking of the earth surface. Sometimes the collapse of the mining can also lead to minor earthquakes especially when it was a deep mine.
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Types of Earthquakes
There are four major types of earthquakes, and these include tectonic earthquakes, volcanic earthquakes, explosion earthquakes, and collapse earthquake.
Tectonic Earthquake
The surface of the earth is mainly made up of the loose fragments which are known as tectonic plates. The tectonic plates are usually in a continuous motion, moving slowly and gradually towards each other ( Chao & Obara, 2016 ). The movement of the plates can take different forms which can be away from each other, towards each other, or past each other. A severe earthquake occurs when the two tectonic plates slide past each other. This kind of earthquake is usually referred to as a tectonic earthquake. This is the most prevalent type of earthquake in the world. Such an earthquake is always severe with huge magnitude and intensity leading to the destruction of properties and loss of lives.
Volcanic Earthquakes
Volcanic earthquakes take place at areas where there is a volcanic eruption. They are usually less prevalent and with less magnitude and intensity as compared to the tectonic earthquake. During an earthquake, magma can erupt from the earth crust leaving behind a void. The void left in the earth crust can be filed by rocks moving downwards. This process of movement of rocks downwards can lead to trembling of the earth surface.
Explosion earthquake
These are earthquakes mainly caused by nuclear explosions. This kind of earthquake is usually triggered by the man during the process of a nuclear explosion. The process of nuclear tests can always result in trembling of the earth surface thus causing an earthquake. However, this kind of earthquake is usually less severe and may not lead to the destruction of properties or loss of life.
Collapse earthquake
This is a kind of earthquake which occur from the collapse of mines. During the mining process. Deep mines may collapse leading to trembling of the earth surface in what is known as collapse earthquake. It is prevalent in areas where mining is prevalent. It is, however, less severe and comes with low intensity as well as magnitude.
Effects of Earthquake
Earthquakes can lead to the destruction of the buildings as well as damage to other properties. Earthquakes that are more severe can always cause damage to many properties while also leading to loss of lives. It can also cause damage to the infrastructure especially when it is severe. Severe earthquakes can also cause landslides. This is especially when the rocks are dislodged thus rolling downwards into the valleys and causing the destruction of properties. Severe earthquake can trigger a tsunami. Tsunami is a long high sea earthquake which is mainly caused by a severe earthquake in the sea areas.
Measurement of Earthquake
Earthquake is usually measured based on the amount of energy that is produced. This is mainly done through the Richter scale. The earthquake can be measured in terms of intensity and magnitude. The Richter scale is used to measure the magnitude of the earthquake as it is produced through seismograph ( Lee et al., 2017 ). The earthquakes with a higher magnitude above seven on the Richter scale usually have serious effects. However, the earthquakes that are below three on the Richter scale tend to have no effect and may not even be felt. Earthquakes which ranges between 3 and 6 on the Richter scale are usually mild.
References
Lomnitz, C. (2013). Global tectonics and earthquake risk (Vol. 5). Elsevier.
Cui, S. H., Huang, R. Q., & Pei, X. J. (2016, June). Geological causes of earthquake induced large landslide: case study of Daguangbao landslide. In Landslides and engineered slopes: experience, theory and practice. Proceedings of the 12th International Symposium on Landslides. Napoli, Italy (pp. 707-714).
Chao, K., & Obara, K. (2016). Triggered tectonic tremor in various types of fault systems of Japan following the 2012 Mw8. 6 Sumatra earthquake. Journal of Geophysical Research: Solid Earth , 121 (1), 170-187.
Lee, W. J., Lu, Z., Jung, H. S., & Ji, L. (2017). Measurement of small co-seismic deformation field from multi-temporal SAR interferometry: application to the 19 September 2004 Huntoon Valley earthquake. Geomatics, Natural Hazards and Risk , 8 (2), 1241-1257.
