The Richter scale matters. Point scale of intensity, strength of earthquakes

History of appearance

The strength of all earthquakes that occur in different parts of our planet is assessed depending on the power of the seismic waves that accompany them. Everything comes down to a single classification system, called the “Richter scale”. It was first proposed by the American seismologist Charles Richter in 1935. Ten years later, together with his colleague Beno Gutenberg, he substantiated his theory, which after that began to be widely used in practice. First of all, the system is designed to characterize the amount of energy produced by the earth's crust. Despite the fact that there are no restrictions on the magnitude scale, a physical limit to its quantity still exists. Actions during an earthquake are determined largely depending on its indicators.

Richter scale indicators

The system proposed by Charles Richter uses a logarithmic scale. Its basic principle is that each of the subsequent integer values indicates an earthquake that is ten times more powerful than the previous one. In other words, for example, if the Richter scale shows that the earth's tremors are 5.0, then this means that they are 10 times stronger than a 4.0 in the same system. However, do not confuse the total energy of an earthquake and its magnitude. When the second increases by one unit, the first increases almost thirty times. According to Richter's theory, earthquake magnitudes correspond to the following characteristics. Shocks that are practically not felt are rated at 2.0 points; weak tremors resulting in minor destruction - 4.5; for moderate damage, a score of 6.0 points is given; The most powerful earthquake known to scientists and ever occurring on the planet was characterized by a mark of 8.5 points on the scale.

Earthquake area

It is a widely known fact that any earthquake consists of one shock or a series of them. They appear due to the occurrence of faults in the earth's crust and the displacement of rock masses along them. Based on the calculations made, the size of the area of rock displacement during barely perceptible tremors is equal to several meters in height and width. In the case when the Richter scale symbolizes tremors with a magnitude of about five points, the size of the foci reaches several kilometers. During the strongest earthquakes with catastrophic consequences, the length of the displacements in depth can be about 50 km - this is with a length of up to one thousand kilometers. The length of the source of the most powerful among all known earthquakes was 1000 km, and the depth was 100 km (a greater value is impossible due to the fact that the earth's substance below this mark is in a state similar to melting).

conclusions

Finally, it should be noted that the Richter scale characterizes the impact that earth tremors exert on the surface. This measurement system demonstrates the damage that has been caused to an area. An earthquake receives its exact score only after the area has been surveyed for surface deformation and destruction of structures. According to experts and scientists, earth tremors with a magnitude of nine or more cannot occur on our planet.

In 1935, Professor C. Richter proposed estimating the energy of an earthquake magnitude(from Latin value).

Magnitude earthquakes - conventional value, characterizing the total energy of elastic vibrations caused by an earthquake. The magnitude is proportional to the logarithm of the energy of earthquakes and allows you to compare vibration sources by their energy.

The magnitude of earthquakes is determined from observations at seismic stations. Ground vibrations that occur during earthquakes are recorded by special devices - seismographs.

The result of recording seismic vibrations is seismogram, on which longitudinal and transverse waves are recorded. Observations of earthquakes are carried out by the country's seismic service. Magnitude M, earthquake intensity in points and focal depth N interconnected (see Table 1) .

Seismologists use several magnitude scales. In Japan they use a scale of seven magnitudes. It was from this scale that Richter K.F. proceeded, proposing his improved 9-magnitude scale. Richter scale- seismic magnitude scale, based on an assessment of the energy of seismic waves arising during earthquakes. The magnitude of the strongest earthquakes on the Richter scale does not exceed 9.

The “magnitude” scale, which reflects the strength of earthquakes, which was proposed by the American seismologist Richter, corresponds to the amplitude of the largest horizontal displacement recorded by a standard seismograph at a distance of 10 km from the epicenter (the point on the earth's surface directly above the focus of the earthquake). The change in this largest horizontal displacement depending on the distance and depth of the earthquake focus (the depth from the surface of the earth to the area where the earthquake originated) is determined using empirical tables and graphs. Magnitudes determined in this way are related to energy by the empirical equation LogE = 11.4 + 1.5 M ,

where M is the magnitude corresponding to the amplitude of the horizontal displacement (Richter, 1958), and E - total energy. In accordance with this dependence, each subsequent unit of the Richter scale means that the released energy is 31.6 times greater than that corresponding to the previous unit of the scale. Other empirically established relationships show that with a unit increase in magnitude, 60 times more energy is released. Therefore, a magnitude 2 earthquake will release 30 to 60 times more energy than a magnitude 1 earthquake, and a magnitude 8 earthquake will release energy that is 8x10 5 -12x10 6 times the energy released by a magnitude 4 earthquake.

Earthquakes with a magnitude of 1 on the Richter scale are usually only responded to by sensitive seismographs. Earthquakes with a magnitude of 2, under suitable conditions, are felt by people in the area of the epicenter. In earthquakes with a magnitude of 4.5 (intensity VI-VII; see Table 6), destruction is observed only in rare cases. For convenience, seismologists refer to earthquakes with a magnitude of 7 or higher on the Richter scale as major earthquakes, with earthquakes with a magnitude of 8 or greater being obviously great earthquakes.

The largest known earthquakes, according to the Richter estimation method, were the 1906 Colombia earthquake and the 1950 Assam earthquake of magnitude 8.6. The estimated magnitude of the 1964 Alaskan earthquake was on the order of 8.4-8.6. It is interesting to note that the focus of all these earthquakes, which had a magnitude, according to Richter, over 8.0, was located at a shallow depth.

Magnitude M, earthquake intensity in points and focal depth h are related to each other (Table 1). The shallower the depth of the source, the greater the intensity of the earthquake in points at the same magnitude values (energy release in the source.)

Approximate ratio of magnitude M and intensity depending on the focal depth h. (Table 1).

Therefore, in everyday life the magnitude value is called Richter scale.

Earthquake magnitude and earthquake intensity rating scale

The Richter scale contains conventional units (from 1 to 9.5) - magnitudes, which are calculated from vibrations recorded by a seismograph. This scale is often confused with earthquake intensity scale in points(according to a 7 or 12-point system), which is based on the external manifestations of an earthquake (impact on people, objects, buildings, natural objects). When an earthquake occurs, it is its magnitude that first becomes known, which is determined from seismograms, and not its intensity, which becomes clear only after some time, after receiving information about the consequences.

Correct usage: « magnitude 6.0 earthquake».

Previous use: « earthquake measuring 6.0 on the Richter scale».

Misuse: « magnitude 6 earthquake», « earthquake measuring 6 magnitudes on the Richter scale» .

Richter scale

$M_s = \lg (A/T) + 1.66 \lg D + 3.30.$

These scales do not work well for the largest earthquakes - when M~8 comes saturation.

Seismic moment and Kanamori scale

The seismic energy released by a nuclear explosion with a power of 1 megaton (1 megaton = 4.184 10 15 J) is equivalent to an earthquake with a magnitude of about 7. It is worth noting that only a small part of the explosion energy is converted into seismic vibrations.

Frequency of earthquakes of different magnitudes

In a year on Earth, approximately:

1 earthquake with a magnitude of 8.0 or higher;
10 - with a magnitude of 7.0-7.9;
100 - with a magnitude of 6.0-6.9;
1000 - with a magnitude of 5.0-5.9.

The strongest recorded earthquake occurred in Chile in 1960—later estimates put Kanamori's magnitude at 9.5.

Write a review of the article "Earthquake Magnitude"

Notes

An excerpt characterizing the magnitude of the earthquake

The historical sea, not as before, was directed by gusts from one shore to another: it seethed in the depths. Historical figures, not as before, rushed in waves from one shore to another; now they seemed to be spinning in one place. Historical figures, who previously at the head of the troops reflected the movement of the masses with orders of wars, campaigns, battles, now reflected the seething movement with political and diplomatic considerations, laws, treatises...
Historians call this activity of historical figures reaction.
Describing the activities of these historical figures, who, in their opinion, were the cause of what they call the reaction, historians strictly condemn them. All famous people of that time, from Alexander and Napoleon to m me Stael, Photius, Schelling, Fichte, Chateaubriand, etc., pass before their strict judgment and are acquitted or condemned, depending on whether they contributed to progress or reaction.
In Russia, according to their description, a reaction also took place during this period of time, and the main culprit of this reaction was Alexander I - the same Alexander I who, according to their descriptions, was the main culprit of the liberal initiatives of his reign and the salvation of Russia.
In real Russian literature, from a high school student to a learned historian, there is not a person who would not throw his own pebble at Alexander I for his wrong actions during this period of his reign.
“He should have done this and that. In this case he acted well, in this case he acted badly. He behaved well at the beginning of his reign and during the 12th year; but he acted badly by giving a constitution to Poland, making the Holy Alliance, giving power to Arakcheev, encouraging Golitsyn and mysticism, then encouraging Shishkov and Photius. He did something wrong by being involved in the front part of the army; he acted badly by distributing the Semyonovsky regiment, etc.”
It would be necessary to fill ten pages in order to list all the reproaches that historians make to him on the basis of the knowledge of the good of humanity that they possess.
What do these reproaches mean?
The very actions for which historians approve of Alexander I, such as: the liberal initiatives of his reign, the fight against Napoleon, the firmness he showed in the 12th year, and the campaign of the 13th year, do not stem from the same sources - the conditions of blood , education, life, which made Alexander’s personality what it was - from which flow those actions for which historians blame him, such as: the Holy Alliance, the restoration of Poland, the reaction of the 20s?
What is the essence of these reproaches?
The fact that such a historical person as Alexander I, a person who stood at the highest possible level of human power, is, as it were, in the focus of the blinding light of all the historical rays concentrated on him; a person subject to those strongest influences in the world of intrigue, deception, flattery, self-delusion, which are inseparable from power; a face that felt, every minute of its life, responsibility for everything that happened in Europe, and a face that is not fictitious, but living, like every person, with its own personal habits, passions, aspirations for goodness, beauty, truth - that this face , fifty years ago, not only was he not virtuous (historians do not blame him for this), but he did not have those views for the good of humanity that a professor now has, who has been engaged in science from a young age, that is, reading books, lectures and copying these books and lectures in one notebook.
But even if we assume that Alexander I fifty years ago was mistaken in his view of what is the good of peoples, we must involuntarily assume that the historian judging Alexander, in the same way, after some time will turn out to be unjust in his view of that , which is the good of humanity. This assumption is all the more natural and necessary because, following the development of history, we see that every year, with every new writer, the view of what is the good of humanity changes; so that what seemed good appears after ten years as evil; and vice versa. Moreover, at the same time we find in history completely opposite views on what was evil and what was good: some take credit for the constitution given to Poland and the Holy Alliance, others as a reproach to Alexander.
It cannot be said about the activities of Alexander and Napoleon that they were useful or harmful, because we cannot say for what they are useful and for what they are harmful. If someone does not like this activity, then he does not like it only because it does not coincide with his limited understanding of what is good. Does it seem good to me to preserve my father’s house in Moscow in 12, or the glory of the Russian troops, or the prosperity of St. Petersburg and other universities, or the freedom of Poland, or the power of Russia, or the balance of Europe, or a certain kind of European enlightenment - progress, I must admit that the activity of every historical figure had, in addition to these goals, other, more general goals that were inaccessible to me.
But let us assume that so-called science has the ability to reconcile all contradictions and has an unchanging measure of good and bad for historical persons and events.
Let's assume that Alexander could have done everything differently. Let us assume that he could, according to the instructions of those who accuse him, those who profess knowledge of the ultimate goal of the movement of mankind, order according to the program of nationality, freedom, equality and progress (there seems to be no other) that his current accusers would have given him. Let us assume that this program was possible and drawn up and that Alexander would act according to it. What would then happen to the activities of all those people who opposed the then direction of the government - with activities that, according to historians, were good and useful? This activity would not exist; there would be no life; nothing would have happened.

- classification of earthquakes by magnitude, based on an assessment of the energy of seismic waves occurring during earthquakes. The scale was proposed in 1935 by the American seismologist Charles Richter (1900‑1985), theoretically substantiated together with the American seismologist Beno Gutenberg in 1941‑1945, and became widespread throughout the world.

The Richter scale characterizes the amount of energy that is released during an earthquake. Although the magnitude scale is not limited in principle, there are physical limits to the amount of energy released in the earth's crust.
The scale uses a logarithmic scale, so that each integer value on the scale indicates an earthquake ten times larger in magnitude than the previous one.

An earthquake with a magnitude of 6.0 on the Richter scale will produce 10 times more ground shaking than an earthquake with a magnitude of 5.0 on the same scale. The magnitude of an earthquake and its total energy are not the same thing. The energy released at the source of an earthquake increases by about 30 times with an increase in magnitude by one unit.
The magnitude of an earthquake is a dimensionless quantity proportional to the logarithm of the ratio of the maximum amplitudes of a certain type of waves of a given earthquake, measured by a seismograph, and some standard earthquake.
There are differences in methods for determining the magnitudes of nearby, distant, shallow (shallow) and deep earthquakes. Magnitudes determined by different types waves differ in size.

Earthquakes of different magnitudes (on the Richter scale) manifest themselves as follows:
2.0 - the weakest felt shocks;
4.5 - the weakest shocks, leading to minor damage;
6.0 - moderate damage;
8.5 - the strongest known earthquakes.

Scientists believe that earthquakes stronger than magnitude 9.0 cannot occur on Earth. It is known that each earthquake is a shock or a series of shocks that arise as a result of the displacement of rock masses along a fault. Calculations have shown that the size of the earthquake source (that is, the size of the area on which the rocks were displaced, which determines the strength of the earthquake and its energy) with weak tremors barely perceptible by humans is measured in length and vertically by several meters.

During earthquakes of medium strength, when cracks appear in stone buildings, the size of the source reaches kilometers. The sources of the most powerful, catastrophic earthquakes have a length of 500-1000 kilometers and go to a depth of up to 50 kilometers. The largest earthquake recorded on Earth has a focal area of 1000 x 100 kilometers, i.e. close to the maximum length of faults known to scientists. A further increase in the depth of the source is also impossible, since earthly matter at depths of more than 100 kilometers goes into a state close to melting.

Magnitude characterizes an earthquake as a single, global event and is not an indicator of the intensity of the earthquake felt at a specific point on the Earth's surface. The intensity or strength of an earthquake, measured in points, not only strongly depends on the distance to the source; Depending on the depth of the center and the type of rock, the strength of earthquakes with the same magnitude can differ by 2-3 points.

The intensity scale (not the Richter scale) characterizes the intensity of the earthquake (the effect of its impact on the surface), i.e. measures the damage caused to a given area. The score is determined when examining the area based on the amount of destruction ground structures or deformations of the earth's surface.

Exists big number seismic scales, which can be reduced to three main groups. In Russia, the 12-point scale MSK-64 (Medvedev-Sponheuer-Karnik), which is the most widely used in the world, is used, dating back to the Mercalli-Cancani scale (1902), in Latin American countries the 10-point Rossi-Forel scale (1883) is adopted, in Japan - 7-point scale.

Intensity assessment based on the everyday consequences of an earthquake, easily distinguishable even by an inexperienced observer, on seismic scales different countries different. For example, in Australia, one of the degrees of shaking is compared to “the way a horse rubs against a veranda post”; in Europe, the same seismic effect is described as “bells begin to ring”; in Japan, “an overturned stone lantern” appears.

The material was prepared based on information from open sources

Richter scale designed to determine the strength of earth vibrations. In other words, the ruler helps to determine the power of earthquakes. The system is international. The Italian Mercalli began to develop it. Who is Richter and why did he take the laurels from his predecessor? We'll find out.

History of the Richter scale

Richter earthquake scale adopted in the 1930s. The Mercalli system was not just renamed, but modified. The Italian was weak for the 12-point basis. Minimum tremors – one.

Earthquakes from 6 points were considered strong. This did not suit all states. In Russia, for example, they focused on 10-point limits, and in Japan on 7-point limits. Meanwhile, the age of globalization has arrived.

A single standard was required so that the data from all seismographs could be understood anywhere on Earth. This is where Charles Richter got involved. The American suggested using the decimal logarithm.

The calculation of the vibration amplitude is directly proportional to the needle deflection on the seismograph. At the same time, Richter introduced a correction in accordance with the distance of the area from the epicenter of the earthquake.

Richter magnitude scale was officially adopted in 1935. The world began to focus not just on 10 points, but also on the 10-point difference between adjacent ruler marks.

A magnitude 2 earthquake is 10 times stronger than a magnitude 1 earthquake. 3-point pushes are 10 times more powerful than 2-point ones, and so on. But how to determine the strength of shaking? How to understand that the movements of the earth’s crust are exactly 3, 7, 9-point?

Richter scale - scores in visual and physical manifestations

The scores help measure the intensity of surface tremors. Their strength is greater in the bowels of the Earth, where the rift occurs. Some of the energy is lost on the way to the solid crust of the planet. It turns out that the closer the source is to the surface, the higher the intensity. 1 point is not noticeable by people.

2 points are recognized only on the upper floors of high-rise buildings; weak vibrations are felt. At 3 points, the chandeliers sway. Noticeable shaking inside buildings, even low-rise ones, is 4 points.

Magnitude 5 earthquakes are detected not only in houses, but also on the street. At 6 points, glass may break, furniture and dishes may move. It becomes difficult to stay on your feet during a magnitude 7 earthquake. By brick walls Cracks spread, stairwells collapse, and landslides form on roads.

At 8 points, buildings are already collapsing, as well as communications laid underground are torn. 9-point tremors lead to disturbances in water bodies and can cause, for example, a tsunami. The soil is cracking.

It crumples and breaks during magnitude 10 earthquakes. 11 points... Stop. After all, the Richter scale ends at ten. In fact of the matter. Gaps in the knowledge of ordinary people led to a mixture of the Mercalli and Richter systems.

The surface intensity of the tremors was measured in points using the Italian scale. She, apparently, did not sink into oblivion, but unofficially joined the American one. Mercalli has both 11 and 12 points.

At 11, brick buildings will collapse to the ground, and only a reminder will remain of the roads. 12 points is a catastrophic earthquake that changes the topography of the earth. The cracks in it reach a width of 10-15 meters.

Now let's figure out what the marks on the true Richter scale indicate. It is “tied” to a magnitude that Mercalli did not take into account. Magnitude determines the energy released during movements in the earth's interior. It is not the external manifestations of the earthquake that are considered, but its internal essence.

Richter scale - magnitude table

While the scores can be determined by observing changes on the surface of the planet, the magnitude is calculated only from seismograph readings. The calculations are based on the type of waves of a typical, average earthquake.

The indicator is put into logarithm with the maximum amplitudes of specific shocks. Magnitude is proportional to this logarithm.

The strength of the energy released during an earthquake depends on the size of its source, that is, the length and width of the fault in the rocks. Typical Richter shocks can be measured not only in whole numbers, but also in fractional numbers.

Thus, a magnitude of 4.5 leads to minor damage. The fault parameters are only a few meters vertically and in length. A source of several kilometers usually produces earthquakes with a magnitude of 6.

The fault is hundreds of kilometers long - magnitude 8.5. There is also a 10 on the Richter scale. But this is, so to speak, an unrealistic limit. There have been no earthquakes with a magnitude greater than 9 on Earth. Apparently it won't happen.

For magnitude 10, a fault depth of more than 100 kilometers is needed. But, at such a depth, the earth is no longer solid, the substance turns into liquid - the mantle of the planet. The length of a ten-fold outbreak should exceed 1000 kilometers. But such faults are not known to scientists.

Earthquakes with a magnitude of 1 do not occur, or rather are not recorded by instruments. The weakest tremors, felt by both seismographs and people, are 2 points. Yes, magnitude indicators are sometimes also called points. But, it is more correct to pronounce only the number, so that there is no confusion with the Mercalli scale.

There is an approximate relationship between the severity of an earthquake and its magnitude. At the same time, it is important to take into account the depth of the shock source. The easiest way to compare the indicators is by looking at the table.

Kilometers	Magnitude
5	5	6	7	8
10	7	8-9	10	11-12
20	6	7-8	9	10-11
40	5	6-7	8	9-10

It can be seen that the same magnitude can lead to different destruction depending on the depth of the source. There are other reasons to judge what it will be like earthquake in points? Richter scale points They also depend on the seismic resistance of buildings in the area of tremors and the nature of the soil.

In good-quality buildings, the force of an earthquake is perceived differently than in houses built without taking into account possible movements of the earth's crust. Charles Richter talked about this back in the 1930s.

The scientist not only created an international scale, but spent his entire life fighting for reasonable construction, taking into account all the risks of a particular area. It was thanks to Richter that many countries tightened building construction standards.