What is an earthquake?
An earthquake is a sudden shaking of the earth's surface caused by tremors. Often people, especially those who do not live in seismically dangerous regions, are mistaken, believing that there is a monolithic indestructible firmament under their feet. But numerous processes are constantly taking place in the bowels of the planet, tectonic plates are shifting, moving forward and pressing on each other. As a result, energy accumulates in the thickness of the Earth for a long time. And one day it is released, causing an earthquake. Scientists have found that the amount of energy released is several thousand times greater than the energy of an atomic bomb, so it is not surprising that an earthquake is accompanied by colossal destruction.
Ninety percent of all major tremors occur in seismically active areas where the edges of the lithospheric plates converge, but sometimes destructive energy can escape where people do not know what an earthquake is. In almost any country, regardless of geographical location and climatic conditions, tremors can be felt at any time of the year. Seismologists can predict the largest earthquakes in advance, butthere is no way to prevent them.
How to measure an earthquake?
What is an earthquake, obviously, but how to measure it? There are two main concepts for this: magnitude and intensity. The magnitude shows the strength of the fluctuations at the very epicenter of the tremors. This value is important for seismologists, but will tell little to ordinary people, because aftershocks with a large magnitude that occurred in the mountains and desert areas will not be particularly destructive. For us, more important is the intensity, measured in points, which characterizes the strength of the above-ground manifestations of an earthquake.
Types of earthquakes
Depending on the causes of tremors, there are several types of earthquakes.
The most common are tectonic earthquakes. They are caused by faults, collisions and movements of tectonic plates. Weak shocks, which are constantly recorded, are practically not felt on the surface. Strong ones cause huge cracks, landslides and landslides to appear on the surface of the earth. They leave massive destruction in their wake. Earthquakes in the sea cause a tsunami and a huge tidal wave.
Volcanic earthquakes caused by volcanic eruptions leave virtually no damage behind. They can be repeated many times until the volcano ceases to act. But "sleeping" volcanoes wake up from time to time.
It often happens in the mountainslandslides and landslides that cause landslide earthquakes that do not have great strength. This happens due to the appearance of voids inside the mountains and underground.
People have a constant impact on the planet and the environment. We build dams, artificially change the course of rivers, turn mountains into plains, drill mines to extract minerals. This cannot but cause consequences, therefore it is not surprising that such an earthquake, as man-made, is provoked by the actions of man himself.
Another type of earthquake is artificial, caused by underground testing of new types of weapons, or resulting from nuclear and other explosions.
