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An earthquake also referred to as a tremor or quake is the trembling that happens on the Earth’s surface as a result of sudden energy release to the Earth’s lithosphere, therefore, developing seismic waves.
Earthquakes vary in size, for instance, some quakes are weak and are not enough to be felt by people or even destroy cities.
However, there are large earthquakes that shake and cause ground displacement. Earthquakes can also result in landslides, property destruction as well as the ground rapture. The largest earthquake is referred to as the main shock and is always followed by aftershocks that are experienced after the mainshock.
The world’s largest earthquake was experienced in 1960 near Valdivia, South Chile, and had around 9.5 magnitudes (Braitenberg and Rabinovich, 2017). This quake is also known as the ‘Great Chilean Earthquake’ that left nearly 2 million people homeless and thousands of buildings destroyed (Braitenberg and Rabinovich, 2017).
Accordingly, it is imperative to understand both causes as well as impacts of earthquakes.
Causes of Earthquakes
Earthquakes happen as a result of various factors such as natural calamities and human activities. In this section, we will go through some of the causes or reasons why earthquakes occur. Before we delve into the details, here is a rundown:
- 1️⃣ Tectonic Movements
- 2️⃣ Volcanic Eruption
- 3️⃣ Human Activities
The Tectonic Movements
Tectonic movements are the disturbance that happens inside the earth. However, this movement creates forces that develop changes on the surface of the earth, and therefore physical features like rift valleys, plateaus, and mountains are created, resulting in seismic waves leading to a tectonic earthquake (Betbeder‐Matibet, 2008).
Many major earthquakes happen because of the tectonic forces that create pressure and tension where stress begins to accumulate inside the earth, hence the term – tectonic earthquakes.
To explain a tectonic earthquake, the Earth contains four main layers that comprise; the inner core, outer core, the earth’s crust, as well as mantle. The crust as well as the upper layer of the mantle creates the thin skin of the planet. Furthermore, these layers of the Earth’s surface are made up of many puzzle-like pieces that are always in a constant slow motion and these puzzle pieces are referred to as tectonic plates (Betbeder‐Matibet, 2008).
The ends of these tectonic plates also referred to as plate boundaries comprise numerous faults and many earthquakes happen on a fault line because the plate boundaries are rough and get trapped while the tectonic plates keep moving. Moreover, when these edges are unstuck from the faults they create an earthquake.
Volcanic Eruption
Earthquakes are also caused by volcanic eruptions. Volcanoes happen as a result of the sudden release of magma. The magma produces forces on the rocks that crack the rock.
Therefore, the magma streams into the cracks and builds up more pressure leading to more cracks resulting in small earthquakes. In addition, when the volcano plumbing system opens up and magma starts flowing out, continuous volcanic earthquakes occur and the produced waves referred to as harmonic tremors are created (Betbeder‐Matibet, 2008).
The volcanic earthquake has been used as a signal to predict eruptions, for instance, the eruptions that happened on Mount St. Helens in 1980 (Betbeder‐Matibet, 2008).
Human Activities
Earthquakes occur through human activities too, particularly by the wastewater produced by the gas and oil drilling operations injected into the ground (Griggs, 2017).
However, this activity does not result in huge quakes although they can cause big impacts. Research by the United States Geological Survey (USGS) about the induced earthquakes suggests that many of the earthquakes that happened in Oklahoma might have been a result of wastewater from the oil industry (Griggs, 2017).
Also, induced seismicity, from a collapse earthquake, can happen through the induction of carbon dioxide produced by fossil fuels and other sources in the Earth’s crust. In addition, man-made earthquakes decrease and increase following industrial activities which are hard to anticipate.
Effects of the Earthquakes
After discussing the major causes of why an earthquake occurs, it is time to take a hard look at the effects of these tremors on both earth’s crust and the earth’s surface.
Following are some major effects of earthquakes:
- 1️⃣ Ground Ruptures & Landslides
- 2️⃣ Death & Injuries
- 3️⃣ Tsunamis
- 4️⃣ Soil Liquefaction
Ground Ruptures and Landslides
Earthquakes bring about massive destruction such as ground rapture as well as landslides. However, the ground rapture is the primary impact that creates seismic waves caused by large earthquakes. The severity of these effects relies on the complex combination of the quake magnitude, geomorphological conditions as well as the distance from the epicenter of the earth’s crust which can reduce or maximize the wave propagation.
Moreover, ground rupture and landslides are major risks to the engineering structures like nuclear power stations and dams as they create new geological faults from primary and secondary waves. For example, in 1970, on the Coast of Peru, an earthquake caused a landslide that started 80 miles far from the quake. This slide was estimated to be nearly 30 meters and killed more than 18,000 individuals (Zeilinga et al., 2011).
Death and Injuries
Moreover, many earthquakes, including volcanic earthquakes, are death-related since they result in construction collapse, broken gas lines, and surface waves leading to the deaths of many people. For instance, in southern Italy, around 100,000 individuals died in 1909 due to earthquakes that happened in this area (Zeilinga et al., 2011).
Many of these people die because of the collapsible structures and others escape this event with severe injuries. Yet, even a minor shaking can result in thousands of casualties whenever a building collapses and also lead to depression and mental consequences for survivors (Zeilinga et al., 2011).
The level of earthquake damage relies on the duration and amplitude of the shaking. Therefore, when the amplitude is large, it results in large earthquakes.
Tsunamis
A tsunami is another effect brought by earthquakes. Tsunamis are harbor waves that happen as a result of the vertical offset of the ocean floor caused by volcanic activity and earthquakes. Sometimes tsunamis rise to nearly 20-25 meters and cause massive damage to people and properties, especially in coastal regions (Zeilinga et al., 2011).
In 1896 in Japan, an earthquake generated a tsunami that destroyed the shore with waves rising to 100 feet and 22,000 people died (Zeilinga et al., 2011).
When an earthquake occurs, the sudden release of energy from the ocean’s elevation then initiates the water waves to travel outside the seafloor region, creating a new fault line. Large waves caused by earthquakes can overrun a coastal region within minutes and also flow in thousands of kilometers in an open ocean causing massive destructions.
Soil Liquefaction
Earthquakes are suggested to result in soil liquefaction (Zeilinga et al., 2011).
This means that, when ground shaking happens, water-saturated materials, for example, the sand lose their strength and turn from solid to liquid. Soil liquefaction results in rigid structures sinking or tilting. For instance, in 1964, this phenomenon made many buildings sink and collapse in the Alaska earthquake (Zeilinga et al., 2011).
Also; other things relying on this soil for support can tilt and collapse.
Conclusion
An earthquake occurs when a sudden vibration and shaking of the surface of the earth is caused by the underground movement of volcanic activity or the movement of tectonic plates. Scientists use seismographs to record seismic waves to determine the intensity of earthquakes.
However, earthquakes cannot be detected and whenever they occur, they can cause massive property damage and even kill people, whether it is a volcanic earthquake or a tectonic earthquake.
Moreover, earthquakes can be caused by human activities particularly the wastewater produced by the gas and oil drilling operations injected into the ground. Earthquakes lead to massive destruction such as ground rapture as well as landslides. It is suggested that there are many deaths as well as severe injuries that happen as a result of earthquakes in many countries.
References
- Betbeder‐Matibet, J. (2008). Causes of Earthquakes. Seismic Engineering, 5-53.
- Braitenberg, C., & Rabinovich, A. B. (2017). The Chile-2015 (Illapel) Earthquake and Tsunami.
- Griggs M. B, 2017. Man-made earthquakes will continue to shake the country. Retrieved from: https://www.popsci.com/2017-earthquake-damage-forecast
- Zeilinga, B. J., Sanders, D. T., & Ballard, R. D. (2011). Volcanoes in Human History: The Far-Reaching Effects of Major Eruptions. Princeton: Princeton University Press.