What Is an Earthquake? Why Do We Have Earthquakes? Read to Know the Answers!
It Is Interesting to Know: All about Earthquakes
Every year thousands of earthquakes happen on our planet. Most of them are not dangerous, as they are so small and insignificant that only special equipment can catch them. But there are more serious vibrations, which usually happen twice a month and are believed to be dangerous for humans.
Where does the earthquake start? Usually, the most shocks of high magnitude occur at the bottom of the world’s oceans. However, unless the earthquake is not accompanied by a huge wave (tsunami), people are not even able to notice them. But when the land shakes, the elements can be so destructive that the number of victims counts in thousands, as it happened in Japan in 2011, when the earthquake caused a tsunami, which resulted in the Fukushima catastrophe. Earthquakes of magnitude 4 to 5 do not cause much damage but are recorded by seismic networks. Earthquakes of magnitude 6 to 7 occur several hundred times a year. Magnitude 8 occurs about ten times a year. The most destructive earthquakes of magnitude 9 occur about once every 30 years. In our blog we have written about many horrible earthquakes, so make sure to read them!
The Earthquake Definition
Well, what is an earthquake? Earthquakes are underground tremors that cause fluctuations in the earth’s surface. These tremors are associated with shifts in the earth’s shells: the crust or the upper mantle. Shifts in the subsurface produce seismic waves – vibrations that propagate through the Earth’s crust, crustal lithosphere, and mantle. Earthquakes can be caused both by nature and by humans. The consequences of high-intensity shocks are often catastrophic. Earthquake is the second-deadliest natural disaster after typhoons.
Unfortunately, at present, scientists have not studied well the processes that take place in the subsoil of our planet, and, sometimes it is hard to explain earthquake reasons and prevent them. Therefore, the forecast of earthquakes is rather approximate and inaccurate.
Why Do We Have Earthquakes?
What causes earthquakes? Among the studied causes of earthquakes, experts and scientists distinguish the next types: tectonic with the underwater earthquakes, volcanic, landslide, and snow slide, artificial and man-made (technogenic) vibrations of the earth’s crust.
Most of the world’s recorded earthquakes are the result of tectonic plate movements when there is a sudden shift of rocks. This can either be a collision of plates with each other or the sinking of a thinner plate beneath another. To delve deeper into information about earthquakes, we should mention the underwater earthquake. They occur when tectonic plates collide either on the ocean floor or near the coast of some continent and usually cause a tsunami. Although this shift is usually only a few centimeters, the mountains above the epicenter are set in motion. Subsequently, the mountains release a gigantic amount of energy, followed by cracks form on the earth’s surface. At the edges of this surface, big tracts of land begin to shift, along with everything on it.
It is impossible not to mention rock slides and large landslides. Usually, these shocks are not strong, but in some cases, their power may be enough to demolish cities and kill people.
Volcanic fluctuations, though weak, but last a long time. Usually, they do not pose a big danger, however, history knows the catastrophic consequences of such earthquakes. As a result of the tremendous eruption of the volcano Krakatoa, the mountain was fully destroyed. This event caused a split of the island into three parts. The tsunami that followed the eruption and the earthquake wiped out everyone left on the island.
Wondering about how do earthquakes happen, you may think that only nature can cause such phenomena. However, in some cases, human activity may be the cause of earthquakes. The fact is, that even technogenic earthquakes have tremendous consequences for the planet and people. Increased cases of the earth shocks were recorded by experts in the areas of large reservoirs. The reason is simple to explain: the collected mass of water starts to press on the underlying crust of the earth, and the water penetrating through the ground begins to demolish it. Additionally, scientists noticed that in places of oil and gas extraction, as well as in the area of mines and quarries an increase in seismic activity may be observed.
Natural disasters can also be induced artificially. Earthquakes are not the exception. For example, after the Democratic People’s Republic of Korea test of its new nuclear weapon in the ocean, the special sensors detected earthquakes with different magnitudes all over the world.