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Is Seoul Earthquake Possible? The year 1999, which is ending, was marked by considerable seismic activity. Devastating earthquakes occurred in Turkey and Taiwan, Greece and Mexico. There is nothing surprising in the fact that now, after all these disasters, the Koreans also began to worry about whether Korea could become a victim of a seismic cataclysm. In general, the Korean Peninsula is an area of ​​rather weak seismic activity. Its southeastern tip is located just a few hundred kilometers from the Pacific Rift. This fault is a huge arc that begins in Alaska and further through the Kuriles, Japan and Taiwan goes far south, to Indonesia and New Zealand. This fault is one of the most seismically unstable regions of the planet. It is constantly shaken by earthquakes, and most of the active volcanoes of the planet are concentrated there. On the other hand, to the east of the Korean Peninsula, on the opposite shore of the Yellow Sea, lies another seismically active zone. It is relatively small, but fraught with considerable troubles (not least because it is located under the most densely populated regions of Northern China). It was here, relatively not far from Beijing, that the most catastrophic earthquake of our century occurred in July 1976, killing 220,000 people. However, despite such a dangerous neighborhood, from the point of view of seismologists, the Korean Peninsula is one of the relatively stable regions. Earthquakes occur here from time to time, but still remain rare. At one time, in the twenties, this circumstance even forced the Japanese government to seriously discuss the issue of transferring the capital of the Japanese Empire to Seoul from seismically unsafe (especially with the construction technique of that time) Tokyo. However, the question arises: is it possible to consider that Korea is in absolute safety? Alas, this is not the case. In the old Korean chronicles there are references to very serious earthquakes, accompanied by both destruction and loss of life. So, in 779, in the Korean capital, which was then located in the city of Gyeongju, in the southeast of the peninsula, "the earth shook, many houses collapsed, and about a hundred people died." In 1455 in Seoul, then already the capital of the country, "buildings collapsed, and many people died under the ruins." Korean scientists, relying on chronicle records, traces of damage on ancient buildings and geological data, have established that over the past two millennia, Korea has experienced about 40 earthquakes of magnitude 7 or more. This is not a very large figure by the standards of, say, Japan or Turkey, but still this figure gives cause for concern. In addition, recent years have witnessed a suspicious increase in seismic activity. If in the 1980s, about 10-15 microearthquakes were registered in Korea per year, then in the 1990s their number roughly doubled. In 1996, 39 earthquakes were recorded in Korea, in 1998 - 32. This year, it seems, will be a record year, since in its first nine months, Korean seismologists recorded 34 earthquakes. It is, of course, about small earthquakes, which are not noticed by people and can only be recorded with special devices. Nevertheless, the growth of seismic activity in Korea is evident. Of particular concern is the fact that the largest focus of seismic activity is located in the Seoul region, that is, where almost half of the country's population is now concentrated. There are also two less serious seismic sources in Korea: in the southeast, in the Daegu and Gyeongju regions, and in the north, near the North Korean capital Pyongyang. Korean seismologists estimate a 57% probability that a large (about 6 points) earthquake will occur in the Seoul area in the next 10 years, roughly the strength of the recent devastating earthquakes in Greece and Taiwan. For Pyongyang and Daegu, this probability is 35% and 29%, respectively. The probability of 57% cannot be called small, so now Korea is taking measures to prepare for a possible earthquake. In particular, after 1988, all houses in the country are being built in such a way as to withstand a five-point earthquake without damage. There are stricter regulations for schools and public buildings. How effective are all these measures? To answer this important question, Korean seismologists and engineers recently conducted simulations of how a hypothetical 6.3 magnitude earthquake would affect an area in central Seoul. According to geologists, two thousand years ago (more precisely, in 89 AD) an earthquake of approximately the same magnitude already occurred on the territory of the current Korean capital. For modeling, an area of ​​1 square kilometer was selected, where there are 780 buildings for various purposes. The analysis showed that about a third of buildings would most likely be badly damaged by an earthquake. At the same time, the most vulnerable were not multi-storey residential complexes built of reinforced concrete, but brick houses 2-4 stories high. In addition, who else, if not us, residents of Russia and the CIS, does not know that any, the most wonderful and most thoughtful standards do not mean anything if they are simply ignored by builders. This, by the way, was the case in Turkey, where most of the houses were built in violation of existing norms. It is clear that it was profitable for entrepreneurs to "save" on building materials, while the Turkish bureaucracy turned out to be ineffective and corrupt, and was ready to turn a blind eye to gross violations of instructions. Be that as it may, but the recent disasters in Turkey and Greece made Koreans think again about the problems of seismic safety. After all, as the Korean press reminds, the cost of preventing destruction is 10-20 times less than the amount that then has to be spent on restoring the destroyed ...

An earthquake is a destructive natural phenomenon, an unpredictable natural disaster that happens suddenly and unexpectedly. An earthquake is a tremor caused by tectonic processes occurring inside the earth, it is vibrations of the earth's surface that occur as a result of sudden ruptures and displacements of parts of the earth's crust. Earthquakes occur anywhere in the world, at any time of the year, it is virtually impossible to determine where and when, and what strength the earthquake will be.

They not only destroy our homes and change the natural landscape, but also demolish cities from the face of the Earth and destroy entire civilizations, they bring fear, grief and death to people.

How the strength of an earthquake is measured

The intensity of the tremors is measured in points. Earthquakes with a magnitude of 1-2 points are captured only by special devices - seismographs.

With an earthquake strength of 3-4 points, vibrations are already captured not only by seismographs, but also by a person - objects around us, chandeliers, flower pots, are swaying, dishes are ringing, doors near cabinets are opening, trees and buildings are swaying, and the person himself is swaying.

At 5 points, it shakes even more, the wall clocks stop, cracks appear on buildings, plaster crumbles.

At 6-7 points, the vibrations are strong, objects, paintings, hanging on the walls, on the window panes and on the walls of stone houses fall, cracks appear.

Earthquakes of magnitude 8-9 lead to the collapse of walls and the destruction of buildings and bridges, even stone houses are destroyed, and cracks form on the surface of the earth.

A 10-point earthquake is more destructive - buildings collapse, pipelines and railway rails burst, landslides and collapses occur.

But the most catastrophic in terms of the power of destruction are earthquakes of 11-12 points.
In a matter of seconds, the natural landscape changes, mountains collapse, cities turn into ruins, huge gaps form in the earth, lakes disappear, and new islands may appear in the sea. But the most terrible and irreparable thing in such earthquakes is that people die.

There is also another more accurate objective way to assess the strength of an earthquake - by the magnitude of the vibrations caused by the earthquake. This value is called magnitude and determines the strength, that is, the energy of the earthquake, the highest value of magnitude-9.

The source and epicenter of the earthquake

The force of destruction also depends on the depth of the earthquake source, the deeper the earthquake source arises from the earth's surface, the less destructive force the seismic waves carry.

The focus arises in the place of displacement of giant rock masses and can be located at any depth from eight to eight hundred kilometers. It does not matter at all whether this displacement is large or not, vibrations of the earth's surface still occur, and how far these vibrations spread depends on their energy and forces.

The greater depth of the earthquake focus reduces destruction on the earth's surface. The destructiveness of an earthquake also depends on the size of the source. If the vibrations of the earth's crust are strong and sharp, then catastrophic destruction occurs on the surface of the Earth.

The epicenter of an earthquake should be considered a point above the source, located on the earth's surface. Seismic or shock waves travel from the source in all directions, the farther from the source, the lower the intensity of the earthquake. The speed of shock waves can reach eight kilometers per second.

Where earthquakes occur most often

What parts of our planet are more earthquake-prone?

There are two zones where earthquakes occur most often. One belt begins at the Sunda Islands and ends at the Isthmus of Panama. This is the Mediterranean belt - it stretches from east to west, passes through mountains such as the Himalayas, Tibet, Altai, Pamir, Caucasus, Balkans, Apennines, Pyrenees and passes through the Atlantic.

The second belt is called the Pacific. These are Japan, the Philippines, it also covers the Hawaiian and Kuril Islands, Kamchatka, Alaska, Iceland. Passes along the western shores of North and South America, through the mountains of California, Peru, Chile, Tierra del Fuego and Antarctica.

There are also seismically active zones on the territory of our country. These are the North Caucasus, Altai and Sayans, the Kuril Islands and Kamchatka, Chukotka and the Koryak Upland, Sakhalin, Primorye and Priamurye, the Baikal zone.

Earthquakes also often occur in our neighbors - in Kazakhstan, Kyrgyzstan, Tajikistan, Uzbekistan, Armenia and other states. And in other areas, which are distinguished by seismic stability, tremors periodically occur.

The seismic instability of these belts is associated with tectonic processes in the earth's crust. Those territories on which there are active smoking volcanoes, where there are mountain ranges and the formation of mountains continues, where earthquake foci are most often located, and tremors often occur in those places.

Why do earthquakes happen

Earthquakes are a consequence of tectonic movement occurring in the depths of our Earth, the reasons for which these movements occur are many - this is the external effect of space, the Sun, solar flares and magnetic storms.

These are the so-called earth waves that periodically arise on the surface of our earth. These waves are clearly visible on the sea surface - sea ebb and flow. They are not noticeable on the earth's surface, but are fixed by instruments. Earth waves cause deformation of the earth's surface.

Some scientists have suggested that the Moon may be the culprit for earthquakes, or rather, the vibrations occurring on the lunar surface, they also affect the earth's surface. Strong destructive earthquakes were observed to coincide with a full moon.

Scientists also note those natural phenomena that precede earthquakes - these are strong, prolonged precipitation, large drops in atmospheric pressure, unusual air glow, restless behavior of animals, as well as an increase in gases - argon, radon and helium and uranium and fluorine compounds in groundwater ...

Our planet continues its geological development, the growth and formation of young mountain ranges occurs, in connection with human activities new cities appear, forests are destroyed, swamps are drained, new reservoirs appear, and the changes that occur in the depths of our Earth and on its surface cause all kinds of natural disasters.

Human activities also have a negative impact on the mobility of the earth's crust. A person who imagines himself to be a tamer and creator of nature, thoughtlessly interferes with the natural landscape - he demolishes mountains, erects dams and hydroelectric power stations on rivers, builds new reservoirs and cities.

And the extraction of minerals - oil, gas, coal, building materials - crushed stone, sand - affects seismic activity. And in those areas where there is a high probability of earthquakes, seismic activity increases even more. By his ill-considered actions, a person provokes landslides, landslides and earthquakes. Earthquakes that occur in connection with human activities are called technogenic.

Another type of earthquake occurs with the participation of humans. With underground nuclear explosions, when tectonic weapons are being tested, or when a large amount of explosives are exploded, vibrations of the earth's crust also occur. The intensity of these tremors is not very high, but they can provoke an earthquake. Such earthquakes are called artificial.

There are still volcanic earthquakes and landslide... Volcanic earthquakes occur due to high voltage in the interior of a volcano, the cause of these earthquakes is volcanic gas and lava. The duration of such earthquakes is from several weeks to several months, they are weak and pose no danger to people.
Landfall earthquakes are caused by large landslides and landslides.

On our Earth, earthquakes occur every day, about one hundred thousand earthquakes a year are recorded by instruments. This incomplete list of catastrophic earthquakes that have occurred on our planet clearly shows what losses humanity suffers from earthquakes.

Catastrophic earthquakes in recent years

1923 - Japan is the epicenter near Tokyo, about 150 thousand people died.
1948 - Turkmenistan, Ashgabat is completely destroyed, about one hundred thousand dead.
1970 in Peru, a landslide caused by an earthquake killed 66,000 residents of the city of Yungai.
1976 - China, the city of Tianshan is destroyed, 250 thousand dead.

1988 - Armenia, the city of Spitak was destroyed -25 thousand people died.
1990 - Iran, Gilan province, 40 thousand dead.
1995 - Sakhalin Island, 2 thousand people died.
1999 - Turkey, the cities of Istanbul and Izmir, 17 thousand dead.

1999 - Taiwan, 2.5 thousand people died.
2001 - India, Gujarat-20 thousand dead.
2003 - Iran, the city of Bam was destroyed, about 30 thousand people died.
2004 - Sumatra Island - earthquake and tsunami caused by the earthquake killed 228 thousand people.

2005 - Pakistan, Kashmir region - 76 thousand people were killed.
2006 - Java Island - 5700 people killed.
2008 - China, Sichuan province, killed -87 thousand people.

2010 - Haiti, 220 thousand people died.
2011 -Japan - earthquake and tsunami, claimed the lives of more than 28 thousand people, the explosions at the Fukushima nuclear power plant led to an environmental disaster.

The most powerful aftershocks destroy the infrastructure of cities, buildings, depriving us of housing, bring colossal damage to the inhabitants of those countries where the elements played out, but the most terrible and irreparable death is the death of millions of people. History keeps the memory of destroyed cities, disappeared civilizations, and no matter how terrible the force of the elements is, a person, having survived a tragedy, restores his housing, builds new cities, erects new gardens and revives the fields on which he grows food for himself.

How to behave during an earthquake

At the first shocks of an earthquake, a person experiences fear, confusion, because everything around is in motion, chandeliers swing, dishes ring, cabinet doors open, and sometimes objects fall, the earth leaves underfoot. Many panic, start to rush, others, on the contrary, hesitate, freeze in place.

If you are on floors 1-2, the first thing you should do is try to leave the room as soon as possible and move to a safe distance from buildings, try to find an open place, pay attention to power lines, you cannot be under them, with strong shocks wires can break and you can get an electric shock.

If you are above the 2nd floor or did not have time to jump out into the street, try to leave the corner rooms. It is better to hide under the table or under the bed, stand in the opening of the internal doors, in the corner of the room, but away from the cabinets and windows, since broken glass and objects in the cabinets, and the cabinets themselves, refrigerators, if they fall, can hurt you and injure you.

If you nevertheless decide to leave the apartment, then be careful, do not enter the elevator, in case of strong earthquakes, the elevator may turn off or collapse, it is also not advised to run to the stairs. Stairways can be damaged by an earthquake, and crowds rushing towards the stairs will increase the load on them and the stairs may collapse. Going out onto balconies is just as dangerous, they can also collapse. Don't jump out of windows.

If tremors hit you outside, move to an open area, away from buildings, from power lines, from trees.

If you are in a car, stop by the side of the road, away from lights, trees, billboards. Don't stop in tunnels, under wires and bridges.

If you live in a seismically active area, and earthquakes periodically shake your homes, then you must prepare yourself and your family for the possibility of a stronger earthquake. Determine in advance the safest areas in your apartment, take measures to strengthen your home, teach children how to behave if children are alone at home during tremors.

Adding some practical data to the above answer about the Gutenberg-Richter relationship, here is a graph of the cumulative probability of earthquakes in a particular province in Japan based on observed frequencies over many hundreds of years:

The relationship is reliably log-linear (according to G-R); if you agree that the ratios will maintain higher values, you estimate the likelihood of an M10 event at that location every 30,000 years.

To get a score for “anywhere in the world,” you need cumulative data for everyone. A good place to start is the USGS website - they have a handy desk with data from 1900.

Taking this data and plotting it on a logarithmic line graph, then extrapolating the linear fit, the following diagram is given:

This is pretty scary because it suggests that the probability of an M10 earthquake anywhere in the world is 1: 100 in any given year. Note that I plotted the data for magnitude x to x.9 at location x), which is a bit underestimating. Note also that in the extreme case of very large earthquakes (8 and above), the data looks like it might deviate from a straight line, but there is not enough data to make any firm conclusions about the shape.

There are a few more caveats. First, it can be assumed that the model can be extrapolated: a particular error cannot be designed to store the energy needed for an M10 event, as it will always release energy before it gets there (and there could be an effect “Stress shadows”, which states that after a large earthquake, the likelihood of another major earthquake is temporarily reduced because the stresses have been relieved, so this model can only be used “for an extended period” and does not accurately reflect the risk of an earthquake in the next five years ).

Nevertheless, it is one percent.

A magnitude 10 earthquake is indeed possible, but very unlikely. You can see that the frequency of the earthquake is determined by the Gutenberg-Richter law:

$$ N = 10 ^ (a-bM) $$

where $ N $ is the number of earthquakes $ \ ge M (magnitude) $ and $ a, b $ are constants. As you can see, the more $ M $, the less $ N $. $ a, b $ are usually solved statistically, through observational data and regression. But at face value, you can easily see that large magnitude earthquakes are becoming less and less frequent at an exponential rate.

What is a magnitude 10 earthquake? My guess is a subduction zone, as this is where the highest earthquakes occur. What is the subduction zone? Any guess is as good as mine, Chile or Tonga, although it is also important to note that the magnitude of the earthquake is often related to the size of the error: I do not think there is an error, long / large, to generate a $ M \ ge 10.0 $ earthquake on The earth is now.

Are 10 magnitude earthquakes possible?

The idea of ​​a Mega Kwaka - an earthquake of magnitude 10 or more - is theoretically possible, very unlikely. earthquake magnitude is partly based on the length of the faults - the longer the error, the larger the earthquake. The simple truth is that there are no known faults that can generate a magnitude of 10 or more Mega Earthquake ()

Where are 10 magnitude earthquakes most likely?

Nine of the ten largest earthquakes to occur in the last century were subduction zone events. This includes the Great Chilean 1960 Earthquake, which at M 9.5 was the largest earthquake ever recorded, the Indian Ocean earthquake and tsunami in 2004, and the 2011 Tōhoku earthquake and tsunami. ()

What is the most likely frequency of a magnitude 10 earthquake?

If they were possible, given that not a single word is recorded in written history, there is no way to forgive sins without great uncertainty. Historical data is misleading. For an explanation see: (1) "This is probably an observational effect that is fairly common in earth sciences." (2) " "

How large are magnitude 10 earthquakes?

Very big. To understand, this pie chart shows how the total seismic moment released by earthquakes for the 1906 -2005 period is with the largest individual earthquakes (left) and groups of earthquakes (right). A thin ribbon of the 1906 San Francisco earthquake is also shown for comparison purposes. M w denotes the magnitude of the earthquake on the timescale.

CAPTION: Global seismic release from 1906 to 2005, the graph shows that almost 25% of the world earthquake energy in a century was concentrated in the Great Chilean Earthquake alone.

This is definitely possible, although not very likely, as mentioned above. An unusually long subduction zone, such as the Peru-Chile trench, Aleutian trench, or Japan-Kamchatka trench, should have eroded generally to call her. In other words, it must be an earthquake that simultaneously hits Russia and Japan, or an earthquake that simultaneously hits Colombia, Ecuador, Peru and Chile, etc.

Also, a Moment Magnitude 10 earthquake will not necessarily be very different in terms of how far the buildings are, say, 8 or 9. However, the shaking will last much longer - about 30 minutes - and will spread over a much larger area. And then of course there are tsunamis that can hit the ground while the shaking is still going on, which greatly increases the damage that an earthquake can cause.

20% of the territory of Russia belongs to seismically active regions (including 5% of the territory is subject to extremely dangerous 8-10 earthquakes).

Over the past quarter century, about 30 significant earthquakes have occurred in Russia, that is, with a force of more than seven on the Richter scale, earthquakes. In the zones of possible destructive earthquakes in Russia, 20 million people live.

The inhabitants of the Far East region of Russia suffer the most from earthquakes and tsunamis. The Pacific coast of Russia is located in one of the "hottest" zones of the "ring of fire". Here, in the area of ​​the transition from the Asian continent to the Pacific Ocean and the junction of the Kuril-Kamchatka and Aleutian island volcanic arcs, more than a third of earthquakes in Russia occur, there are 30 active volcanoes, including such giants as Klyuchevskaya Sopka and Shiveluch. It has the highest distribution density of active volcanoes on Earth: there is one volcano for every 20 km of the coast. Earthquakes occur here no less frequently than in Japan or Chile. Seismologists usually count at least 300 tangible earthquakes a year. On the map of seismic zoning of Russia, the regions of Kamchatka, Sakhalin and the Kuril Islands belong to the so-called eight- and nine-point zone. This means that in these areas the intensity of shaking can reach 8 or even 9 points. Destruction may also be appropriate. The most devastating earthquake measuring 9 on the Richter scale occurred on Sakhalin Island on May 27, 1995. About 3 thousand people died, the city of Neftegorsk, located 30 kilometers from the epicenter of the earthquake, was almost completely destroyed.

The seismically active regions of Russia also include Eastern Siberia, where 7-9-point zones are distinguished in the Baikal region, the Irkutsk region and the Buryat Republic.

Yakutia, through which the border of the Euro-Asian and North American plates passes, is not only considered a seismically active region, but also holds a record: earthquakes with epicenters north of 70 ° N are often observed here. As seismologists know, the main part of earthquakes on Earth occurs in the equator and in the middle latitudes, and in high latitudes such events are recorded extremely rarely. For example, on the Kola Peninsula, a wide variety of traces of high-power earthquakes have been found, mostly quite old. The forms of the seismogenic relief discovered on the Kola Peninsula are similar to those observed in the zones of earthquakes with an intensity of 9-10 points.

Other seismically active regions of Russia include the Caucasus, the spurs of the Carpathians, the shores of the Black and Caspian Seas. These areas are characterized by earthquakes with a magnitude of 4-5. However, during the historical period, catastrophic earthquakes with a magnitude of more than 8.0 were also noted here. Traces of a tsunami were also found on the Black Sea coast.

However, earthquakes can occur in areas that cannot be called seismically active. On September 21, 2004, in Kaliningrad, two series of tremors with a force of 4-5 points were recorded. The epicenter of the earthquake was located 40 kilometers southeast of Kaliningrad in the area of ​​the Russian-Polish border. According to the maps of the general seismic zoning of the territory of Russia, the Kaliningrad region belongs to a seismic safe area. Here, the probability of exceeding the intensity of such shaking is about 1% over 50 years.

Even residents of Moscow, St. Petersburg and other cities located on the Russian Platform have reason to worry. On the territory of Moscow and the Moscow region, the last of such seismic events with a force of 3-4 points took place on March 4, 1977, on the night from August 30 to August 31, 1986 and on May 5, 1990. The strongest known seismic tremors in Moscow, with an intensity of more than 4, were observed on October 4, 1802 and November 10, 1940. These were the "echoes" of the larger earthquakes in the Eastern Carpathians.