On what scale is the intensity of an earthquake assessed? Earthquakes

An earthquake is a physical vibration of the lithosphere - the solid shell of the earth's crust, which is in constant motion. Often such phenomena occur in mountainous areas. It is there that underground rocks continue to form, causing the Earth's crust to be especially mobile.

Causes of the disaster

The causes of earthquakes can be different. One of them is the displacement and collision of oceanic or continental plates. During such phenomena, the surface of the Earth vibrates noticeably and often leads to the destruction of buildings. Such earthquakes are called tectonic. They may form new depressions or mountains.

Volcanic earthquakes occur due to the constant pressure of hot lava and all kinds of gases on the earth's crust. Such earthquakes can last for weeks, but, as a rule, they do not cause massive destruction. In addition, such a phenomenon often serves as a prerequisite for a volcanic eruption, the consequences of which can be much more dangerous for people than the disaster itself.

There is another type of earthquake - landslide, which occurs for a completely different reason. Groundwater sometimes forms underground voids. Under the pressure of the earth's surface, huge sections of the Earth fall down with a roar, causing small vibrations that can be felt many kilometers from the epicenter.

Earthquake scores

To determine the strength of an earthquake, they generally resort to either a ten- or twelve-point scale. The 10-point Richter scale determines the amount of energy released. The 12-point Medvedev-Sponheuer-Karnik system describes the impact of vibrations on the Earth's surface.

The Richter scale and the 12-point scale are not comparable. For example: scientists detonate a bomb underground twice. One at a depth of 100 m, the other at a depth of 200 m. The energy expended is the same, which leads to the same Richter rating. But the consequence of the explosion - displacement of the crust - has varying degrees of severity and has different effects on the infrastructure.

Degree of destruction

What is an earthquake from the point of view of seismic instruments? A one-point phenomenon is determined only by the equipment. 2 points can be sensitive animals, and also, in rare cases, especially sensitive people located on the upper floors. A score of 3 feels like the vibration of a building caused by a passing truck. A magnitude 4 earthquake causes slight rattling of glass. With five points, the phenomenon is felt by everyone, and it does not matter where the person is, on the street or in a building. An earthquake of magnitude 6 is called strong. It terrifies many: people run out into the street, and mother-in-laws form on some walls of houses. A score of 7 leads to cracks in almost all houses. 8 points: architectural monuments, factory chimneys, towers are knocked over, and cracks appear in the soil. 9 points lead to severe damage to houses. Wooden buildings either topple over or sag heavily. Magnitude 10 earthquakes lead to cracks in the ground up to 1 meter thick. 11 points is a disaster. Stone houses and bridges are collapsing. Landslides occur. No building can withstand 12 points. With such a catastrophe, the topography of the Earth changes, river flows are diverted and waterfalls appear.

Japanese earthquake

A destructive earthquake occurred in the Pacific Ocean, 373 km from the capital of Japan, Tokyo. This happened on March 11, 2011 at 14:46 local time.

A magnitude 9 earthquake in Japan led to massive destruction. The tsunami that hit the country's east coast flooded large parts of the coastline, destroying houses, yachts and cars. The height of the waves reached 30-40 m. The immediate reaction of people prepared for such tests saved their lives. Only those who left home in time and found themselves in a safe place were able to avoid death.

Japan earthquake victims

Unfortunately, there were no casualties. The Great East Japan Earthquake, as the event became officially known, claimed 16,000 lives. 350,000 people in Japan were left homeless, leading to internal migration. Many settlements were wiped off the face of the Earth, and there was no electricity even in large cities.

The earthquake in Japan radically changed the habitual way of life of the population and greatly undermined the economy of the state. The authorities estimated the losses caused by this disaster at $300 billion.

What is an earthquake from the point of view of a Japanese resident? It is a natural disaster that keeps the country in constant turmoil. The looming threat forces scientists to invent more accurate instruments for detecting earthquakes and more durable materials for building buildings.

Affected Nepal

On April 25, 2015, at 12:35 p.m., an almost 8-magnitude earthquake that lasted 20 seconds occurred in central Nepal. The following happened at 13:00. Aftershocks lasted until May 12. The reason was a geological fault on the line where the Hindustan plate meets the Eurasian plate. As a result of these tremors, the capital of Nepal, Kathmandu, moved to the south by three meters.

Soon the whole earth learned about the destruction that the earthquake brought in Nepal. Cameras installed directly on the street recorded the moment of the tremors and their consequences.

26 districts of the country, as well as Bangladesh and India, felt what an earthquake was like. Authorities are still receiving reports of missing people and collapsed buildings. 8.5 thousand Nepalese lost their lives, 17.5 thousand were injured, and about 500 thousand were left homeless.

The earthquake in Nepal caused real panic among the population. And it’s not surprising, because people lost their relatives and saw how quickly what was dear to their hearts collapsed. But problems, as we know, unite, as was proven by the residents of Nepal, who worked side by side to restore the former appearance of city streets.

Recent earthquake

On June 8, 2015, an earthquake of magnitude 5.2 occurred in Kyrgyzstan. This is the last earthquake to exceed magnitude 5.

Speaking about a terrible natural disaster, one cannot fail to mention the earthquake on the island of Haiti, which occurred on January 12, 2010. A series of tremors ranging from magnitude 5 to 7 claimed 300,000 lives. The world will remember this and other similar tragedies for a long time.

In March, the shores of Panama experienced a magnitude 5.6 earthquake. In March 2014, Romania and southwestern Ukraine learned the hard way what an earthquake is. Fortunately, there were no casualties, but many experienced anxiety before the disaster. In recent years, earthquake scores have not crossed the brink of catastrophe.

Earthquake Frequency

So, the movement of the earth's crust has various natural causes. Earthquakes, according to seismologists, occur up to 500,000 annually in different parts of the Earth. Of these, approximately 100,000 are felt by people, and 1,000 cause serious damage: they destroy buildings, highways and railways, break power lines, and sometimes carry entire cities underground.

Richter scale was invented to determine the strength of earth vibrations. In other words, it will help us determine the power of earthquakes. This system is international. It was invented by the Italian Mercalli. Who was Richter and why did he get all the laurels?

History of the Richter scale

Richter earthquake scale developed in the thirties of the twentieth century. The Mercalli system was not only renamed, but also completed. The Italian used a 12-point scale as a basis. The minimum tremors were equal to one.

Earthquakes of magnitude 6 or higher were considered strong. Not all states agreed with this. , for example, they used a 10-point scale, and in Japan a 7-point scale. But in the age of globalization, everything has changed.

A common standard was needed, and the data from all seismographs could be deciphered anywhere on Earth. This is where Charles Richter got down to business. The American began to use the decimal logarithm.

The measurement of the vibration amplitude was directly proportional to the change in the needle on the seismograph. Richter also made adjustments depending on the distance of the area from the epicenter of the earthquake.

Richter magnitude scale was officially registered in 1935. The world began to focus not only on 10 points, but also on the difference of ten points between adjacent marks on the ruler.

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

Richter scale - scores in visual and physical manifestations

The scores will help us measure the frequency of surface tremors. Their power in the bowels of the Earth, where the fault occurred, is greater. Part of the energy leaves on the way to the solid crust of the planet. This means that the closer the source is to the surface, the greater the power. People don't feel one point.

Two points will be felt only by residents of the upper floors of high-rise buildings, feeling weak vibrations. At three points the chandeliers swing. Perceptible shaking inside buildings, even small ones, is four points.

And five-magnitude earthquakes are felt not only in houses, but also on the streets. At six points, glass may crack, furniture and dishes may move. It becomes difficult to stand on your feet during a magnitude 7 earthquake. Cracks spread along brick walls, flights of stairs can be destroyed, and landslides occur on roads.

With eight points, buildings can be destroyed, as well as communications located underground can be torn. Nine-magnitude tremors lead to disturbances on the water and can cause a tsunami. The soil is cracking.

It crushes and breaks it during magnitude 10 earthquakes. Eleven points... Stop. After all, the Richter scale ends at ten. In fact of the matter. Gaps in people's knowledge led to the mixing of the Mercalli and Richter systems.

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

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

What do the marks on the true Richter scale tell us? It is based on magnitude, which Mercalli did not take into account. Magnitude measures the energy released during movements in the earth's interior. They consider not the external manifestations of an earthquake, but their internal essence.

Richter scale - magnitude table

While it is possible to determine the scores by observing changes on the surface of the planet, the magnitude is measured only using seismograph readings. The calculation is based on the type of waves of a typical, average earthquake.

The indicator is put in a logarithm with the maximum amplitude 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 fractions.

Thus, a magnitude of 4.5 leads to minor damage. The parameters of the fault 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 ten on the Richter scale. But this is, so to speak, an unrealistic limit. There have been no earthquakes on Earth with a magnitude greater than 9. 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.

The table shows 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 strong 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.

Related Posts

Lithospheric plates. Click to enlarge.

Earthquakes are tremors and vibrations of the Earth's surface caused by natural causes (mainly tectonic processes) or artificial processes (explosions, filling of reservoirs, collapse of underground cavities in mine workings). Small tremors can also cause lava to rise during volcanic eruptions.

About a million earthquakes occur throughout the Earth each year, but most are so small that they go unnoticed. Really strong earthquakes, capable of causing widespread destruction, occur on the planet about once every two weeks. Fortunately, most of them occur on the bottom of the oceans, and therefore are not accompanied by catastrophic consequences (if an earthquake under the ocean does not occur without a tsunami).

Earthquakes are best known for the devastation they can cause. Destructions of buildings and structures are caused by soil vibrations or giant tidal waves (tsunamis) that occur during seismic displacements on the seabed.
The International Earthquake Observation Network records even the most distant and low-magnitude earthquakes.

Tectonic fault map

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Click to enlarge

Earthquake Safety Measures

The commander of the American international rescue team, who has participated in rescue operations in 60 countries, criticizes the common rules of behavior during an earthquake.

As reported by Bakililar.AZ, the commander of the American international rescue team, Rescue Chief and Disaster Manager of the American Rescue Team International (ARTI), Doug Cope, based on his observations, compiled rules of behavior that increase the chances of survival.

He penetrated into 875 earthquake-damaged buildings, worked on rescue teams in 60 countries, for 2 years I was a UN disaster expert, and since 1985, not a single major disaster has gone unnoticed by him.

“The first building I managed to get into was a school in Mexico City during the 1985 earthquake. All the children were under their desks. They were all flattened to the thickness of their own bones.

They could have been saved if they had been lying next to the desks in the aisles. It’s unthinkable, from my point of view, but children were ordered to hide under tables and desks during the earthquake.

I was surprised, but in Mexican schools, the Duck and Cover instruction is still in effect, bend over, cover your head with your hands and hide under the table,” says Cope.

When a building collapses, a heavy ceiling falls onto an object or furniture, destroying it and creating a cavity or empty space nearby.

Cope calls it the “triangle of life.” The larger and stronger the object, the larger the cavity where a person can avoid injury and escape. This can be seen on TV when we see rescue teams working.

10 rules for surviving an earthquake:

1) Anyone who ducked and took cover in a collapsing building or car would be injured or killed.

2) Cats, dogs and babies often adopt a natural womb position. This is what you need to do during an earthquake. It's instinct. This position helps to fit into a small cavity.

Move closer to a large, bulky object that, if crushed or flattened, will still leave some space for survival.

3) Wooden buildings are the safest during earthquakes. Wood works well in bending and torsion under the influence of a seismic wave.

If a wooden building does collapse, it creates large escape cavities and does not cause major injuries. Brick buildings are destroyed into individual bricks.

Bricks cause significant injuries, but still less than concrete ones. Concrete panel buildings are the most dangerous during earthquakes.

4) If an earthquake catches you in bed at night, just roll out of bed. The safest place will be around the bed. In hotels, many lives could be saved if instructions were posted on every room door instructing visitors to lie on the floor near the bottom of the bed during an earthquake.

5) If an earthquake occurs and you cannot escape through the door or window, lie on the floor in the womb position next to the bed or large chair.

6) Almost everyone standing in the doorway of the falling building was killed. How? If you stand under a door lintel, when the door frame collapses, you will be destroyed along with it

7) Never stand on steps during an earthquake. The steps have a separate torsional moment from the building frame.

The steps and other debris of the building, constantly colliding, simply grind the person inside this massacre.

Even if the building doesn't collapse, don't stay on the steps. Even if the steps are intact, they can be destroyed by the influx of many people and should be checked first.

If possible, it is better to be near external walls inside or outside the building. Better outside than inside. The further away from the outside wall you are inside the building, the less chance you have of jumping out.

9) People inside vehicles die when upper-level roads collapse on them. Almost all of the victims of the San Francisco earthquake were inside vehicles.

If they had been sitting or lying next to the vehicles they would have been saved. Each destroyed vehicle has a 3-foot-tall safety cavity next to it, unless a pillar falls directly onto the vehicle.

10) From the experience of breaking into a newspaper office, it became clear that stacks of paper form the largest security cavities.

Earthquake strength

When an earthquake occurs, its energy is released in various forms: mechanical, thermal, electric and magnetic field energy, etc. This energy is enormous, and determining its full extent is proving to be quite a challenge. Most of the mechanical energy is spent on the destruction of rock in the focal area of ​​the earthquake, on the vertical and horizontal displacement of adjacent blocks of the earth's crust. And only a small part of this energy is radiated in all directions into the surrounding space in the form of seismic waves that spread across the globe. When the waves reach the Earth's surface, they generate those ground vibrations that we perceive as an earthquake.

To characterize the strength of earthquakes, concepts such as magnitude, energy class and intensity .

Magnitude (M) earthquake is a conventional measure of energy released from the earthquake source in the form of seismic waves. The amplitude of a seismic wave refers to the displacement of the ground, and the greater the amplitude of the wave, the greater the magnitude of the earthquake.

The concept of magnitude was introduced in 1935 by American seismologist Charles Richter, a professor at the California Institute of Technology in Pasadena.

Let's define Richter's magnitude in his own words:

“The magnitude of any shock is determined as the logarithm, expressed in microns, of the maximum amplitude of the record of that shock made by a standard short-period twisting seismometer at a distance of 100 km from the epicenter.”

In practice, measurements are made at different distances from the epicenter using different instruments. Therefore, amendments are used to bring to the necessary conditions.

There are various magnitude scales around the world, differing in the way they are determined. These are local magnitude (ML), surface wave magnitude (MS), body wave magnitude (mb), and seismic moment magnitude (MW). The maximum magnitude value on the scale introduced by Richter is about 9 units. Minimal earthquakes, still noticeable without instruments, are characterized by a magnitude in the range of 2–3. Earthquakes of smaller magnitudes are recorded only by sensitive seismic instruments.

Soil vibrations during earthquakes with magnitudes differing by one differ in the amplitudes of seismic waves by a factor of 10. Thus, earthquakes noticeable without instruments, ranging from barely perceptible to catastrophic and destructive, differ in wave amplitudes by at least millions of times. With seismic energy values, released during earthquakes, the energy of atomic and hydrogen explosions is comparable.

In our country, as in other countries of the former Soviet Union, another characteristic of the magnitude of an earthquake is used, equivalent magnitude and called energy class (TO).

Energy classes of earthquakes vary in the range from 0 to 18–20. On average around the world, the following formula is used to convert magnitudes into values ​​of energy classes K:

K = 4+1.8M

In turn, the energy class is related to seismic energy by a simple relationship:

E = 10 K Joules

Therefore, magnitude can be related to seismic energy as follows:

log E = 4 + 1.8M

Intensity - a fundamentally different characteristic of the strength of an earthquake, established only during tangible tremors at each specific point on the Earth’s surface on a descriptive and, as a rule, non-instrumental scale. Intensity characterizes the manifestation of an earthquake on the Earth's surface; it depends on the magnitude of the earthquake, the depth of the source and soil conditions and is measured in points.

In seismology, intensity is synonymous with intensity.

The intensity is greater the closer the source is to the surface, so, for example, if the source of an earthquake with a magnitude of 8 is located at a depth of 10 km, then on the surface the intensity will be XI–XII points; at the same magnitude, but at a depth of 40–50 km, the impact on the surface decreases to IX–X points.

Seismic scales . Seismic movements are complex, but can be classified. There are a large number of seismic scales, which can be reduced to three main groups. The most widely used in the world is used in Russia. XII-point scale MSK-64 (Medvedev-Sponheuer-Karnik), in Latin American countries the X-point Rossi-Forel scale is adopted, in Japan - VII-point scale.

The intensity assessment, which is based on everyday manifestations of an earthquake, which are easily distinguishable even by an inexperienced observer, is different on the seismic scales of different countries. For example, in Australia, one degree of shaking is compared to “the sound of a horse rubbing against a veranda post”; in Europe, the same seismic effect is described as “bells starting to ring”; in Japan, “an overturned stone lantern” appears. In the simplest and most convenient form, sensations and observations are presented in a schematized short descriptive scale (MSK version) that can be used by anyone.

MSK-64 scale

The manifestations of the same earthquake at different points are different - from the most intense in the epicentral region to the minimal in the distance. Thus, magnitude is a certain quantity characterizing the energy at the source of an earthquake, and intensity is a measure of the strength of seismic shaking at the observation point, depending not only on the intensity of seismic waves emitted from the source, but also on the distance to the epicenter, depth of the source, location point and ground features at that point. This can be clearly seen in the figure below.

Magnitude is given in conventional units that reflect the source energy (or intensity at the source) of the earthquake. Intensity (or severity) determines the degree of shaking and disturbance on the surface.

Journalists make the mistake of reporting:“The strength of the earthquake is 7 points on the Richter scale,” because. with a magnitude of 7 on the Richter scale, the intensity of the earthquake on the surface, if the source is shallow, can be X points, as was the case, for example, in Spitak (Armenia) in 1988. If the source is located at a sufficient depth, then with the same magnitude 7 the intensity on the surface can be only VIII, as was the case with the Zaisan earthquake (Kazakhstan) in 1990.

To better navigate newspaper and television reports about earthquakes that have occurred, you can use the following simple table by N.V. Shebalina.

Scientists believe that earthquakes stronger than magnitude 9 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 volume in which the rocks were displaced) with weak tremors barely perceptible by humans is measured in several meters. During earthquakes of medium strength, when cracks appear in buildings, the size of the source reaches kilometers. The sources of the most powerful, catastrophic earthquakes have a length of 500–1000 km or even more and go to a depth of up to 50 km. The largest earthquake recorded on Earth has a focal size close to the maximum length of faults known to scientists. A further increase in the depth of the source is also impossible, since the earth's matter at depths of more than 100 km in the mantle passes into a semi-molten state. Consequently, an earthquake such as the one that occurred in Southeast Asia (Sumatra) in December 2004 and had a magnitude of 9 can be considered close to the maximum in its strength. The length of the rupture at the source of this earthquake was estimated at 1200–1300 km, and its width was more than 100 km.

How often do earthquakes of this magnitude occur? Seismology is a relatively young science. She is just over 100 years old. But she has already accumulated enough data to draw some statistical conclusions, which are shown in the following table:

Data on the frequency of earthquakes with a magnitude of 9 are not given here. However, it is clear that they occur even less frequently. Since 1900, only 5 events with this magnitude have been recorded on Earth.

BIBLIOGRAPHY:

1. A.A. Nikonov. Earthquakes... Past, present, forecast. M.: KomKniga. 2006. 192 p.
2. A. Nurmagambetov, M.S. Kunaev. Physics of the Earth. Almaty: KazNTU. 2007. 224 p.
3. J. Geer, H. Shah. Shaky ground: What is an earthquake and how to prepare for it. M.: Mir. 1988. 220 p.
4. HELL. Zavyalov. Earthquake off the coast of Sumatra // Nature. 2005. No. 5

Ilyina Vera Vasilievna, Candidate of Physical and Mathematical Sciences, Professor Kaz GASA,
Art. teacher of the Republican Advanced Training Courses for management personnel in the field of emergency situations and civil defense of the Ministry of Emergency Situations of the Republic of Kazakhstan

It is estimated that millions of people are registered on our planet every year. earthquakes. Of course, the vast majority of them are not felt by people; many do not cause serious damage, but several times a year the planet “shakes in a big way”, the news of which immediately spreads across news channels. Unfortunately, journalists often make mistakes when using scientific terms in their reports. One of them will be discussed in this article.

All reports of seismic disasters are usually accompanied by words like “... an earthquake measuring 6.9 on the Richter scale occurred.” This formulation is incorrect. Interestingly, this kind of error can also be found in some educational literature.

Typically, in popular scientific descriptions of earthquakes, two common terms appear: earthquake severity and magnitude.

Earthquake intensity characterizes the intensity of ground shaking during an earthquake (sometimes they say “earthquake intensity”). It is assessed on a special scale. The first of them appeared in the second half of the 19th century. In 1902 it was developed Mercalli-Cancani scale, long considered one of the best. It is outdated and is not used today, but it was on its basis that almost all modern 12-point scales were created, including the most common one today international Medvedev-Sponheuer-Karnik scale (MSK-64). It is used to estimate the intensity of earthquakes in most countries of the world. You can see a brief explanation of this scale in the table.

There are other scales. For example, in Latin American countries they use ten-point Rossi-Forel scale, created in 1883. In Japan they use 8-point Japan Meteorological Agency scale. For a comparison of the three most common scales, see diagram 1.

The intensity of an earthquake usually decreases as it moves away from the epicenter.

Earthquake Magnitude characterizes the total energy of seismic vibrations of the earth's surface. Magnitude is defined as “the logarithm of the ratio of the maximum wave amplitudes of a given earthquake to the amplitudes of the same waves of some standard earthquake” (the magnitude of a “standard earthquake” is taken as 0). The magnitude scale was first proposed in 1935 by C. Richter, which is why people still often talk about "magnitude on the Richter scale", which is inaccurate. The Richter scale approximates modern formulas for calculating magnitude, but is not currently used.

A change in magnitude by one means an increase in the amplitude of vibrations by 10 times and an increase in the amount of released energy by 32 times.

Unlike intensity, magnitude does not have a unit of measurement - it is denoted by a whole number or a decimal fraction, so saying "magnitude 6.9" is incorrect. Intensity is determined by subjective indicators: people’s feelings, damage to structures, changes in terrain, while the determination of magnitude is based on strict physical and mathematical calculations. We can draw the following analogy: the magnitude of an earthquake is the offhand estimated force of the explosion (determined by external manifestations), and the magnitude is the power of the explosive device. However, it should be remembered that magnitude is not an absolute value of earthquake energy, it is just a relative characteristic. To determine the actual energy of an earthquake based on its magnitude, a special formula is used.

It is estimated that the energy of a magnitude 7.2 earthquake corresponds to the energy of the explosion of a megaton atomic bomb. The strongest earthquake in the entire history of observations occurred in 1960 in Chile, its magnitude was 9.5 (according to the magazine Around the World and Wikipedia). In many sources you can find other information: the magnitude of the largest earthquake was about 8.9-9.0. Most likely, these differences are associated with inaccuracies in calculations (the error in determining the magnitude can reach 0.25).

Another interesting question: are there any limitations to the magnitude scale? There are no mathematical ones, but there is some physical limit to the energy of an earthquake on our planet. Unfortunately, it was not possible to find any references to such studies. If you manage to come across such information, please let us know by sending a letter to This email address is being protected from spambots. You must have JavaScript enabled to view it. .

As for another type of earthquakes, which also occur occasionally - earthquakes caused by the fall of meteorites, asteroids and other cosmic bodies to the Earth, the research results here are very disappointing. Astronomers estimate that the magnitude of the earthquake caused by the impact of a large asteroid could be 13, meaning its energy would be a million times greater than the energy of the largest known earthquake. But this event is still unlikely, so, most likely, by the time such a threat looms, humanity will be ready to prevent it.

Thus, the following conclusions can be drawn. The example of a typical message placed at the beginning of the article is a classic example of a mishmash of terms. It's correct to say this:

“An earthquake of magnitude 6.9 occurred,”

or, if we are talking about points

“An earthquake with an intensity of 8 points (on the MSK-64 scale) occurred.”

In conclusion: Are earthquakes possible in the Urals? The answer is simple: possible. Despite the fact that the Ural Mountains are old, and their territory does not belong to seismic belts, tectonic movements of the earth’s crust are still preserved here. Seismologists annually record up to five earthquakes of magnitude 2-3 in the Urals. The strongest earthquake in the Urals happened less than a century ago in 1914, its magnitude was about 7 points. According to the seismic zoning map of the world (

Earthquakes vary in strength and impact on the earth's surface. And science has repeatedly attempted to classify them according to these indicators.

As a result of such attempts, 12-point scales were developed, based on an assessment of their impact on the earth's surface.

12-point scale for assessing the intensity of earthquakes (hereinafter earthquake scale) estimates the intensity of an earthquake in points at a given point, regardless of its power at the epicenter.

Richter scale has a different approach and estimates the amount of seismic energy released at the epicenter of an earthquake. The unit of seismic energy is magnitude.

12 point earthquake scale.

In 1883, 12 ball earthquake scale was designed by Giuseppe Mercali. Later it was improved by the author himself, and subsequently also by Charles Richter (the author of the Richter scale) and was called the Modified Mercalli Earthquake Scale.

This earthquake scale is currently used in the United States.

In the USSR and Europe, the 12-point earthquake scale - MSK-64 - was used for a long time. According to it, as well as the Mercalli earthquake scale, their intensity is measured in points indicating the intensity, nature and scale of the impact on the surface of the earth, buildings, people and animals in a given area.

The MSK-64 earthquake scale is very clear. And if we hear in the media that an earthquake with a magnitude of 6 occurred, we can very easily imagine that, according to this earthquake scale, it was strong and was felt by all people. Many of them ran out into the street. Pieces of plaster fell off and paintings fell from the walls.

Or a 9.0 magnitude earthquake can be imagined as devastating, in which stone houses were damaged and destroyed, and wooden houses were knocked down.

Everything is simple and clear.

It should be noted that according to the earthquake scale, their intensity is assessed at a certain point. It is clear that at the epicenter located above the source of the earthquake and at a distant point its intensity will be different.

In 1988, the European Seismic Committee began updating the MSK-64 earthquake scale and in 1996, an updated earthquake scale called EMS-98, along with a manual for use, was recommended for use. This earthquake scale is also 12 point and has no fundamental differences with other earthquake scales.

In Japan, the earthquake scale of the Japan Meteorological Agency is used. It starts at three points when people begin to feel the points.

It describes in separate columns the impact on people, on the environment inside buildings and on the street. The highest rating on this earthquake scale is 7.

It is also not fundamentally different from other scales.

Richter scale. Magnitude.

Often, including in the media, you can hear about an earthquake occurring somewhere with a force of, for example, 6 points on the Richter scale.

This is not true. The Richter scale does not describe the intensity of an earthquake, expressed in points, but a completely different characteristic, expressed in other units.

The Richter scale estimates the amount of released seismic energy at the epicenter based on the amplitude of soil vibrations measured by instruments that reached the measurement point. This value is expressed in magnitude.

Richter himself defined the magnitude of any shock as: “the logarithm, expressed in microns, of the amplitude of the recording of this shock made by a standard short-period twisting seismometer at a distance of 100 kilometers from the epicenter.”

Magnitude calculated after measuring the amplitude on the seismogram. And when making calculations, it is necessary to make corrections: for the depth of the earthquake source, for the fact that the measurements were carried out with a non-standard seismometer. It is necessary to bring the calculations to those measured at a standard distance of 100 km from the epicenter.

This is not an easy calculation. And due to the listed difficulties, the magnitude values ​​​​produced by different sources may differ slightly.

But in general, they will give an objective assessment of the power of the earthquake.

Therefore, it would be correct to say that an earthquake with a magnitude of, say, -5 on the Richter scale occurred in a certain place.

Magnitude, calculated at different points on the Richter scale will have the same value. The intensity of the shocks in points at different points will be different.

This is the difference between the 12-point earthquake scale and the 9.5-point Richter scale, expressed in magnitude (the Richter scale has a range of 1 - 9.5 magnitude).

You should not confuse (and this happens all the time in the media) the concepts of the Richter scale and the 12-point earthquake scale.

The intensity on the Richter scale is determined immediately from the readings of seismographs. The intensity in points is determined later, based on an assessment of the impact on the earth's surface. Therefore, the very first reports on assessing the power of shocks come precisely on the Richter scale.

How to correctly report the intensity of tremors in magnitude on the Richter scale?

The correct usage is “an earthquake of magnitude 7 on the Richter scale.”

Previously, due to an oversight, the incorrect expression was used - “an earthquake of 7 points on the Richter scale.”

Or it’s also incorrect - “an earthquake of magnitude 7 on the Richter scale” or “magnitude 7 on the Richter scale.”

The Richter scale describes the power of tremors at the epicenter, regardless of conditions, and introduces a unit of measurement for the power of tremors - magnitude. Other scales describe their impact on the surface in different places depending on conditions, soils, rocks, distance from the epicenter, etc.

For this reason Richter scale is the most objective and scientifically based.

Richter scale(joke)