Thanks to modern technology, scientists were able to calculate how many earthquakes occur on our planet every year. They are fixed more than a million. Most of them are not felt by people because of their small magnitude, but there are those that become a real disaster.
And what is the magnitude of earthquakes and how is it measured? How do scientists manage to determine which of the phenomena will cause damage and which will remain imperceptible?
Magnitude
Scientists have developed special scales that measure the strength of tremors. To understand what earthquake magnitude is, it is necessary to familiarize yourself with the magnitudes of the measurements of this phenomenon.
There are several types of scales: Mercalli - Kankani, Medvedev - Shponkhoyer - Karnik, Richter. Thanks to them, it is clear what magnitude is. This is a number that can be measured by a specific reference indicator. During the next earthquake, it is customary to talk about balality and magnitude.
Magnitude Scale
For the longest time, the Mercalli – Kankani grid was considered the very first scale. Nowadays, it is an outdated model, so the value of tremors is not measured by it.
However, on its basis all modern methods for assessing the strength of blows have been developed, including the international scale MSK 64 (Medvedev - Shponkhoyer - Karnik). It is taken in most countries of the world to analyze the intensity of the phenomenon.
MSK 64
This rating system is represented by a twelve-point scale. From it you can find out what characterizes the magnitude of the earthquake:
- 1 point Such phenomena are not felt by people, but their devices are fixed.
- 2 points. In some cases, they can be observed by people, most often on the upper floors of buildings.
- 3 points. Blows are noticeable to those with high sensitivity.
- Earthquake 4 points. Glass rattling is noted.
- 5 points. It is considered a sufficiently noticeable earthquake, in which individual objects can swing.
- 6 points. Cracks in buildings.
- 7 points. Heavy objects may fall. Large cracks appear in the walls of buildings.
- 8 points. The houses are partially collapsing.
- 9 points. Buildings and other structures are crumbling.
- 10 points. Deep cracks appear in the soil, old structures are completely destroyed.
- 11 points. Numerous cracks appear on the surface of the earth, landslides occur in the mountains. Buildings are completely destroyed.
- 12. The relief is seriously changing, and the buildings are completely destroyed.
Richter score
In 1935, the scientist C. Richter suggested that magnitude is the energy of seismic waves. Based on this statement, he developed a special scale on which the tremor activity is still being evaluated.
The Richter magnitude scale characterizes the amount of energy released during seismological activity. It uses a logarithmic scale, where each value indicates a push ten times the previous one. For example, if an earthquake of 4 points is recorded, then the phenomenon will cause a tenfold stronger oscillation than the magnitude of 3 points on the same scale.
According to Richter, seismological activity is measured as follows:
1.0-2.0 - is fixed by devices;
2.0-3.0 - weak sensations of tremors;
3.0 - chandeliers in houses swing;
4-5 - tremors are weak, but can cause minor damage;
6.0 - tremors that can cause moderate damage;
7 - it is difficult to stand on one's feet, cracks begin to go along the walls, staircases can be destroyed;
8.5 - very strong earthquakes that can cause relief changes.
9 - causes a tsunami, the soil cracks heavily.
10 - fault depth of one hundred or more kilometers.
Earthquakes in history
One of the most powerful earthquakes in the world was seismological activity recorded in 1960 in Chile. On the Richter scale, devices indicated significant activity. Then the Chileans learned what magnitude is 8.5 points. Shocks caused a tsunami with a ten-meter wave height.
Four years later, in the northern part of the Alaskan Gulf, shocks of magnitude 9 were recorded. Due to this activity of the plates, there has been a strong change in the coastline of some islands.
Another powerful earthquake occurred in 2004 in the Indian Ocean. On a Richter scale, he was assigned 9 points. The shocks caused a severe tsunami with a wave height of more than fifteen meters.
In 2011, in Japan, an earthquake occurred that caused a huge tragedy: thousands of people died and the nuclear power plant was destroyed.
Unfortunately, such disasters are not uncommon. How to prevent earthquakes, scientists still do not know.