The question of where an earthquake might occur is relatively simple to answer. Seismic maps have existed for a long time, on which seismically active zones of the globe are marked (Fig. 17). These are those areas of the earth's crust where tectonic movements occur especially often.

It should be noted that the epicenters of earthquakes are localized in very narrow zones, which, according to some scientists, determine the interacting edges of lithospheric plates. There are three main seismic belts - Pacific, Mediterranean and Atlantic. About 68% of all earthquakes occur in the first of them. It includes the Pacific coast of America and Asia and, through a system of islands, reaches the coasts of Australia and New Zealand. The Mediterranean belt stretches in a latitudinal direction - from the Cape Verde Islands through the Mediterranean coast, the south of the Soviet Union to Central China, the Himalayas and Indonesia. Finally, the Atlantic Belt runs along the entire underwater Mid-Atlantic Ridge from Spitsbergen and Iceland to Bouvet Island.

Rice. 17. Layout of seismically active zones of the globe. 1, 2, 3 - shallow, intermediate and deep points, respectively.

On the territory of the Soviet Union, about 3 million square kilometers are occupied by seismically dangerous areas, where earthquakes of magnitude 7 or more are possible. These are some areas of Central Asia, the Baikal region, and the Kamchatka-Kuril ridge. The southern part of Crimea is seismically active, where the 8-magnitude Yalta earthquake of 1927 has not yet been forgotten. The regions of Armenia are no less active, where a strong 8-magnitude earthquake also occurred in 1968.

In all seismically active zones, earthquakes are possible; in other places they are unlikely, although not excluded: some Muscovites may remember how a 3-magnitude earthquake occurred in our capital in November 1940.

It is relatively easy to predict where an earthquake will occur. It is much more difficult to say when it will happen. It has been noticed that before an earthquake, the slope of the earth's surface, measured by special instruments (tilt meters), begins to change rapidly, and in different directions. A “tilt storm” occurs, which can serve as one of the harbingers of an earthquake. Another way of forecasting is to listen to the “whisper” of rocks, those underground noises that appear before an earthquake and intensify as it approaches. Highly sensitive instruments detect an increase in the local electric field - the result of rock compression before an earthquake. If on the coast after tremors the water level in the ocean changes sharply, then a tsunami must be expected.

Nadezhda Guseva

Candidate of Geological and Mineralogical Sciences

Is it possible to predict earthquakes?

Predicting earthquakes is a difficult task. Vertical and horizontal displacements of blocks of the earth's crust cause deep earthquakes, which can reach catastrophic force. Low-hazard surface earthquakes occur due to the fact that the magmatic melt rising along cracks in the earth's crust stretches these cracks as it moves. The problem is that these two related but different causes of earthquakes have similar external manifestations.

Tongariro National Park, New Zealand

Wikimedia Commons

However, a team of scientists from New Zealand was able not only to distinguish traces of stretching of the earth's crust caused by magmatic and tectonic processes in the Tongariro deep fault zone, but also to calculate the rate of stretching arising from one and other processes. It has been established that in the area of ​​the Tongariro fault, magmatic processes play a secondary role, and tectonic processes have a decisive influence. The results of the study, published in the July issue of the Bulletin of the Geological Society of America, help clarify the risks of dangerous earthquakes in this popular tourist park, located 320 kilometers from the capital of New Zealand, Wellington, as well as in similar structures in other regions of the Earth.

Grabens and rifts

Tongariro is New Zealand's Yellowstone. Three “smoking mountains” - volcanoes Ruapehu (2797 meters), Ngauruhoe (2291 meters) and Tongariro (1968 meters), many smaller volcanic cones, geysers, lakes painted in blue and emerald colors, stormy mountain rivers together form a picturesque landscape of the national Tongariro Park. These landscapes are familiar to many because they served as natural settings for Peter Jackson’s film trilogy “The Lord of the Rings.”

By the way, the origin of these beauties is directly related to the peculiarities of the geological structure of the region: with the presence of parallel faults in the earth’s crust, accompanied by the “falling through” of the fragment located between the faults. This geological structure is called a graben. A geological structure that includes several extended grabens is called a rift.

Planetary-scale rift structures pass through the median axes of the oceans and form mid-ocean ridges. Large rifts serve as the boundaries of tectonic plates, which, like the hard segments that make up a turtle's shell, form the hard shell of the Earth, its crust.

New Zealand formed where the Pacific Plate is slowly subducting under the Australian Plate. The chains of islands that appear in such zones are called island arcs. On a planetary scale, rift zones are extension zones, and island arc zones are compression zones of the Earth's crust. However, on a regional scale, stresses in the earth's crust are not monotonic, and in each major compression zone there are local extension zones. As a very rough analogy of such local tensile zones, we can consider the occurrence of fatigue cracks in metal products. The Tongoriro Graben is such a local extension zone.

In New Zealand, due to its position in a zone of active geological processes on a planetary scale, about 20 thousand earthquakes occur every year, approximately 200 of them are strong.

Magma or tectonics?

Earthquake forecasting is difficult. Faults often serve as channels through which magma moves from deep levels to the surface. This process is also accompanied by local stretching of the earth's crust. In this case, magma does not always reach the earth's surface, and in some cases it can stop at a certain depth and crystallize there, forming a long and narrow magmatic body called a dike.

On the surface, extensions of the earth's crust caused by the intrusion of dikes (extensions of a magmatic nature) are often morphologically indistinguishable from extensions caused by the release of stresses arising due to the movement of blocks of the earth's crust relative to each other (extensions of a tectonic nature). But to predict earthquakes, it is critically important to distinguish between these two types of stretching, because earthquakes associated with the intrusion of dikes are near-surface and do not lead to catastrophic consequences, while earthquakes of a tectonic nature can cause a lot of trouble.

It was clear that both types of extension took place in the New Zealand rift system, and in particular in the Tongoriro graben, but there were two mutually contradictory opinions as to which of them predominated.

Threat of catastrophic earthquakes

The research, undertaken by a team including Geological Survey New Zealand and Auckland and Massey universities, was carried out to find a way to distinguish between magmatic and tectonic extension and clarify the risks of large and catastrophic earthquakes in Tongariro National Park.

The scientists used a combination of methods, including relative geochronology to determine the sequence of faults in the earth's crust and analysis of historical records of volcanic eruptions. The key stage of the study was the numerical modeling of the parameters of disturbances in the earth's crust that would arise as a result of the intrusion of dikes, and a careful comparison between the model and actually observed parameters.

The study concluded that the crust in the Tongoriro graben region is stretching by 5.8–7 mm per year due to tectonic events and by 0.4–1.6 mm per year due to volcanic eruptions and dyke intrusions. This means that magmatic processes are not the main cause of crustal movements and building codes must take into account the possibility of strong and catastrophic earthquakes. And the developed methodology can be used to assess the contribution of magmatic processes to the movements of the earth’s crust in similar structures in other regions of the Earth.

Today, science is moving forward with great strides, and people can predict and forecast many natural phenomena in advance, including natural disasters. An earthquake is one of the most dangerous manifestations of the nature of our planet; it can cause enormous damage. Is it possible to predict such geological disturbances today? How do scientists do this? The answers to these questions are of interest to many people, primarily those who live in seismically hazardous areas.

Science has provided humanity with certain capabilities in predicting geological disasters, although predictions are not always 100% accurate. It's worth talking about how they are made.

What causes earthquakes?

Earthquakes are a consequence of geological processes occurring in the mantle and crust. Lithospheric plates move, and in normal situations this movement is barely noticeable. However, stress accumulates on crustal faults due to uneven movements, which ultimately causes earthquakes. These phenomena are not observed everywhere; they are characteristic of geologically turbulent places at the junctions of the earth's crust. The most unstable place is the so-called “ring of fire”, stretching along the outskirts of the Pacific Ocean. It frames the largest lithospheric plate on the planet, on which this ocean is located.

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Earthquakes and volcanoes

Any, even the slightest, movement of such a mass of the earth’s crust cannot occur painlessly, so earthquakes occur constantly along its periphery. There is also massive volcanic activity there.

Predictions of earthquakes in the past

People have long sought to predict natural disasters. The first successful steps in this direction were made thousands of years ago in geologically turbulent regions. In China, ancient scientists were able to create an unusual vase, which was found by modern archaeologists during excavations. Ceramic dragons sit on the edge of the vase, each holding a ball in its mouth. At the slightest vibrations of the earth, harbingers of an impending earthquake, balls fell out of the mouths of the dragons - first of all, from the direction of the source of the future earthquake. This way people could find out in time about an imminent disaster, and even about which side the source of the cataclysm would be located.

Japan also had its own developments - this country has always been a turbulent place. Here people relied more on observations of nature. Before an earthquake, bottom fish rise to the upper layers of water; catfish show particular concern. This was noticed by fishermen, who each time in such cases hurried home to warn their loved ones about the impending disaster.

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Interesting fact: Catfish in Japanese legends is seen as a fish symbolizing earth and stability. Perhaps this is due precisely to the fact that in a calm geological situation the fish swims peacefully and slowly at the bottom, and before earthquakes it begins to rush around and look for shelter.

It was also noted that the fire burning on a candle or splinter sharply goes down before earthquakes, and the candle burns out very quickly. This is due to geomagnetic changes that occur before a cataclysm. Also everywhere, people noted the anxiety of pets and their desire to leave the house before a disaster. Based on these and other signs, people of the past often managed to save themselves, their loved ones or property by leaving their homes and cities in time.

Modern methods of earthquake prediction

Today, seismographs are used to prevent earthquakes. These devices are particularly sensitive sensors that record any vibrations on the surface of the earth. Since microshocks are first observed before any earthquake, the device gives fairly accurate predictions. He records these warning signs and transmits the information to scientists, who warn people through the media. Today, every individual can have their own small seismograph at their disposal - there are individual seismic monitors on sale that record changes and transmit them within a network, which allows you to receive warnings and send them.

Not a year goes by without a catastrophic earthquake happening somewhere, causing total destruction and casualties, the number of which can reach tens and hundreds of thousands. And then there is the tsunami - abnormally high waves that arise in the oceans after earthquakes and wash away villages and cities along with their inhabitants on the low shores. These disasters are always unexpected; their suddenness and unpredictability are frightening. Is modern science really unable to foresee such cataclysms? After all, they predict hurricanes, tornadoes, weather changes, floods, magnetic storms, even volcanic eruptions, but with earthquakes - complete failure. And society often believes that scientists are to blame. Thus, in Italy, six geophysicists and seismologists were put on trial for failing to predict the earthquake in L'Aquila in 2009, which claimed the lives of 300 people.

It would seem that there are many different instrumental methods and instruments that record the slightest deformations of the earth’s crust. But the earthquake forecast fails. So what's the matter? To answer this question, let's first consider what an earthquake is.

The uppermost shell of the Earth - the lithosphere, consisting of a solid crust with a thickness of 5–10 km in the oceans and up to 70 km under mountain ranges - is divided into a number of plates called lithospheric. Below is also the solid upper mantle, or more precisely, its upper part. These geospheres consist of various rocks that have high hardness. But in the thickness of the upper mantle at different depths there is a layer called asthenospheric (from the Greek asthenos - weak), which has a lower viscosity compared to the above and underlying mantle rocks. It is assumed that the asthenosphere is the “lubricant” through which lithospheric plates and parts of the upper mantle can move.

During their movement, the plates collide in some places, forming huge folded mountain chains; in others, on the contrary, they split to form oceans, the crust of which is heavier than the crust of the continents and is capable of sinking under them. These plate interactions cause enormous stress in rocks, compressing or, conversely, stretching them. When stresses exceed the tensile strength of rocks, they undergo very rapid, almost instantaneous displacement and rupture. The moment of this displacement constitutes an earthquake. If we want to predict it, we must give a forecast of place, time and possible strength.

Any earthquake is a process that occurs at a certain finite speed, with the formation and renewal of many different-scale ruptures, the ripping up of each of them with the release and redistribution of energy. At the same time, it is necessary to clearly understand that rocks are not a continuous homogeneous massif. It has cracks, structurally weakened zones, which significantly reduce its overall strength.

The speed of propagation of a rupture or ruptures reaches several kilometers per second, the destruction process covers a certain volume of rocks - the source of the earthquake. Its center is called the hypocenter, and its projection onto the Earth's surface is called the epicenter of the earthquake. Hypocenters are located at different depths. The deepest ones are up to 700 km, but often much less.

The intensity, or strength, of earthquakes, which is so important for forecasting, is characterized in points (a measure of destruction) on the MSK-64 scale: from 1 to 12, as well as by magnitude M, a dimensionless value proposed by Caltech professor C. F. Richter, which reflects the amount of released total energy of elastic vibrations.

What is a forecast?

To assess the possibility and practical usefulness of earthquake forecasting, it is necessary to clearly define what requirements it must meet. This is not guessing, not a trivial prediction of obviously regular events. A forecast is defined as a scientifically based judgment about the place, time and state of a phenomenon, the patterns of occurrence, spread and change of which are unknown or unclear.

The fundamental predictability of seismic disasters has not raised any doubts for many years. Belief in the limitless predictive potential of science was supported by seemingly quite convincing arguments. Seismic events with the release of enormous energy cannot occur in the bowels of the Earth without preparation. It should include certain restructuring of the structure and geophysical fields, the greater the more intense the expected earthquake. Manifestations of such restructuring - anomalous changes in certain parameters of the geological environment - are detected by methods of geological, geophysical and geodetic monitoring. The task, therefore, was to, having the necessary techniques and equipment, timely record the occurrence and development of such anomalies.

However, it turned out that even in areas where continuous careful observations are carried out - in California (USA), Japan - the strongest earthquakes happen unexpectedly every time. It is not possible to obtain a reliable and accurate forecast empirically. The reason for this was seen in insufficient knowledge of the mechanism of the process under study.

Thus, the seismic process was considered a priori to be predictable in principle if the mechanisms, evidence and necessary techniques, unclear or insufficient today, are understood, supplemented and improved in the future. There are no fundamentally insurmountable obstacles to forecasting. The postulates of the limitless possibilities of scientific knowledge, inherited from classical science, and the prediction of processes of interest to us were, until relatively recently, the initial principles of any natural scientific research. How is this problem understood now?

It is quite obvious that even without special research it is possible to confidently “predict”, for example, a strong earthquake in the highly seismic zone of transition from the Asian continent to the Pacific Ocean in the next 1000 years. It can be just as “reasonably” stated that in the area of ​​Iturup Island in the Kuril Ridge tomorrow at 14:00 Moscow time there will be an earthquake with a magnitude of 5.5. But the price for such forecasts is a pittance. The first of the forecasts is quite reliable, but no one needs it due to its extremely low accuracy; the second is quite accurate, but also useless, because its reliability is close to zero.

From this it is clear that: a) at any given level of knowledge, an increase in the reliability of the forecast entails a decrease in its accuracy, and vice versa; b) if the forecast accuracy of any two parameters (for example, the location and magnitude of an earthquake) is insufficient, even an accurate prediction of the third parameter (time) loses practical meaning.

Thus, the main task and main difficulty of predicting an earthquake is that predictions of its location, time and energy or intensity would satisfy the practical requirements at the same time in terms of accuracy and reliability. However, these requirements themselves vary depending not only on the achieved level of knowledge about earthquakes, but also on the specific forecasting goals that are met by different types of forecast. It is customary to highlight:

• seismic zoning (seismicity estimates for decades - centuries);
• forecasts: long-term (for years - decades), medium-term (for months - years), short-term (in time 2-3 days - hours, in place 30-50 km) and sometimes operational (in hours - minutes).

The short-term forecast is especially relevant: it is this that is the basis for specific warnings about the upcoming disaster and for urgent actions to reduce the damage from it. The cost of mistakes here is very high. These errors are of two types:

1. A “false alarm” is when, after taking all measures to minimize the number of casualties and material losses, the predicted strong earthquake does not occur.
2. “Missing the target” when the earthquake that took place was not predicted. Such errors are extremely common: almost all catastrophic earthquakes are unexpected.

In the first case, the damage from disrupting the rhythm of life and work of thousands of people can be very large; in the second, the consequences are fraught not only with material losses, but also with human casualties. In both cases, the moral responsibility of seismologists for an incorrect forecast is very high. This forces them to be extremely careful when issuing (or not issuing) official warnings to the authorities about the impending danger. In turn, the authorities, realizing the enormous difficulties and dire consequences of stopping the functioning of a densely populated area or large city for at least a day or two, are in no hurry to follow the recommendations of numerous “amateur” unofficial forecasters who declare 90% and even 100% reliability your predictions.

The high price of ignorance

Meanwhile, the unpredictability of geocatastrophes is very costly for humanity. As Russian seismologist A.D. Zavyalov notes, for example, from 1965 to 1999 earthquakes accounted for 13% of the total number of natural disasters in the world. From 1900 to 1999, there were 2,000 earthquakes with a magnitude greater than 7. In 65 of them, M was greater than 8. Human losses from earthquakes in the 20th century amounted to 1.4 million people. Of these, in the last 30 years, when the number of victims began to be calculated more accurately, there were 987 thousand people, that is, 32.9 thousand people per year. Among all natural disasters, earthquakes rank third in terms of the number of deaths (17% of the total number of deaths). In Russia, on 25% of its area, where there are about 3,000 cities and towns, 100 large hydro and thermal power plants, five nuclear power plants, seismic shocks with an intensity of 7 or more are possible. The strongest earthquakes in the twentieth century occurred in Kamchatka (November 4, 1952, M = 9.0), in the Aleutian Islands (March 9, 1957, M = 9.1), in Chile (May 22, 1960, M = 9.5 ), in Alaska (March 28, 1964, M = 9.2).

The list of the strongest earthquakes in recent years is impressive.

2004, December 26. Sumatra-Andaman earthquake, M = 9.3. The strongest aftershock (repeated shock) with M = 7.5 occurred 3 hours 22 minutes after the main shock. In the first 24 hours after it, about 220 new earthquakes with M > 4.6 were registered. The tsunami hit the coasts of Sri Lanka, India, Indonesia, Thailand, Malaysia; 230 thousand people died. Three months later, an aftershock with M = 8.6 occurred.

2005, March 28. Nias Island, three kilometers from Sumatra, earthquake with M = 8.2. 1300 people died.

2005, October 8. Pakistan, earthquake with M = 7.6; 73 thousand people died, more than three million were left homeless.

2006, May 27. Java Island, earthquake with M = 6.2; 6,618 people died, 647 thousand were left homeless.

2008, May 12. Sichuan Province, China, 92 km from Chengdu, earthquake M = 7.9; 87 thousand people were killed, 370 thousand were injured, 5 million were left homeless.

2009, April 6. Italy, earthquake with M = 5.8 near the historical city of L'Aquila; 300 people became victims, 1.5 thousand were injured, more than 50 thousand were left homeless.

2010, January 12. Haiti Island, a few miles off the coast, two earthquakes with M = 7.0 and 5.9 within a few minutes. About 220 thousand people died.

2011, March 11. Japan, two earthquakes: M = 9.0, epicenter 373 km northeast of Tokyo; M = 7.1, epicenter 505 km northeast of Tokyo. Catastrophic tsunami, more than 13 thousand people died, 15.5 thousand went missing, destruction of the nuclear power plant. 30 minutes after the main shock - an aftershock with M = 7.9, then another shock with M = 7.7. During the first day after the earthquake, about 160 shocks with magnitudes from 4.6 to 7.1 were registered, of which 22 shocks with M > 6. During the second day, the number of registered aftershocks with M > 4.6 was about 130 (of which 7 aftershocks with M > 6.0). During the third day, this number dropped to 86 (including one shock with M = 6.0). On the 28th day, an earthquake with M = 7.1 occurred. By April 12, 940 aftershocks with M > 4.6 were recorded. The epicenters of the aftershocks covered an area about 650 km long and about 350 km across.

All of the listed events, without exception, turned out to be unexpected or “predicted” not so definitely and accurately that specific safety measures could be taken. Meanwhile, statements about the possibility and even repeated implementation of a reliable short-term forecast of specific earthquakes are not uncommon both in the pages of scientific publications and on the Internet.

A Tale of Two Forecasts

In the area of ​​the city of Haicheng, Liaoning Province (China), in the early 70s of the last century, signs of a possible strong earthquake were repeatedly noted: changes in the slopes of the earth's surface, geomagnetic field, soil electrical resistance, water level in wells, and animal behavior. In January 1975, the impending danger was announced. By the beginning of February, the water level in the wells suddenly rose, and the number of weak earthquakes increased greatly. By the evening of February 3, the authorities were notified by seismologists of an imminent disaster. The next morning there was an earthquake with a magnitude of 4.7. At 14:00 it was announced that an even stronger impact was likely. Residents left their homes and security measures were taken. At 19:36, a powerful shock (M = 7.3) caused widespread destruction, but there were few casualties.

This is the only example of a surprisingly accurate short-term forecast of a destructive earthquake in time, location and (approximately) intensity. However, other, very few forecasts that came true were insufficiently definite. The main thing is that the number of both unpredicted real events and false alarms remained extremely large. This meant that there was no reliable algorithm for stable and accurate prediction of seismic disasters, and the Haicheng forecast was most likely just an unusually successful coincidence of circumstances. So, a little more than a year later, in July 1976, an earthquake with M = 7.9 occurred 200–300 km east of Beijing. The city of Tangshan was completely destroyed, killing 250 thousand people. There were no specific harbingers of the disaster, and no alarm was declared.

After this, as well as after the failure of a long-term experiment to predict the earthquake in Parkfield (USA, California) in the mid-80s of the last century, skepticism prevailed about the prospects for solving the problem. This was reflected in most of the reports at the meeting “Evaluation of Earthquake Forecast Projects” in London (1996), held by the Royal Astronomical Society and the Joint Association of Geophysics, as well as in the discussion of seismologists from different countries on the pages of the journal "Nature"(February - April 1999).

Much later than the Tangshan earthquake, the Russian scientist A. A. Lyubushin, analyzing geophysical monitoring data of those years, was able to identify an anomaly that preceded this event (in the upper graph of Fig. 1 it is highlighted by the right vertical line). The anomaly corresponding to this catastrophe is also present in the lower, modified graph of the signal. Both graphs contain other anomalies that are not much worse than the one mentioned, but do not coincide with any earthquakes. But no precursor to the Haicheng earthquake (left vertical line) was initially found; the anomaly was revealed only after modifying the graph (Fig. 1, bottom). Thus, although it was possible to identify the precursors of the Tangshan and, to a lesser extent, Haicheng earthquakes a posteriori in this case, a reliable predictive identification of signs of future destructive events was not found.

Nowadays, analyzing the results of long-term, since 1997, continuous recordings of the microseismic background on the Japanese Islands, A. Lyubushin discovered that even six months before the strong earthquake on the island. Hokkaido (M = 8.3; September 25, 2003) there was a decrease in the time-average value of the precursor signal, after which the signal did not return to its previous level and stabilized at low values. Since mid-2002, this has been accompanied by an increase in the synchronization of the values ​​of this characteristic at different stations. From the standpoint of catastrophe theory, such synchronization is a sign of the approaching transition of the system under study to a qualitatively new state, in this case, an indication of an impending disaster. These and subsequent results of processing the available data led to the assumption that the event on the island. Hokkaido, although strong, is just a foreshock of an even more powerful upcoming catastrophe. So, in Fig. Figure 2 shows two anomalies in the behavior of the precursor signal - sharp minima in 2002 and 2009. Since the first of them was followed by an earthquake on September 25, 2003, the second minimum could be a harbinger of an even more powerful event with M = 8.5–9. Its place was indicated as “Japanese Islands”; it was more accurately determined retrospectively, after the fact. The time of the event was first predicted (April 2010) for July 2010, then from July 2010 for an indefinite period, which excluded the possibility of declaring an alarm. It happened on March 11, 2011, and, judging by Fig. 2, it could have been expected earlier and later.

This forecast refers to the medium-term ones, which have been successful before. Short-term successful forecasts are always rare: it was not possible to find any consistently effective set of precursors. And now there is no way to know in advance in what situations the same precursors will be effective as in A. Lyubushin’s forecast.

Lessons from the past, doubts and hopes for the future

What is the current state of the problem of short-term seismic forecasting? The range of opinions is very wide.

In the last 50 years, attempts to predict the location and time of strong earthquakes within a few days have been unsuccessful. It was not possible to identify the precursors of specific earthquakes. Local disturbances of various environmental parameters cannot be precursors of individual earthquakes. It is possible that a short-term forecast with the required accuracy is generally unrealistic.

In September 2012, during the 33rd General Assembly of the European Seismological Commission (Moscow), the Secretary General of the International Association of Seismology and Physics of the Earth's Interior P. Sukhadolk admitted that breakthrough solutions in seismology are not expected in the near future. It was noted that none of the more than 600 known precursors and no set of them guarantee the prediction of earthquakes, which occur without precursors. It is not possible to confidently indicate the place, time, and power of the cataclysm. Hopes are pinned only on predictions where strong earthquakes occur with some frequency.

So is it possible in the future to increase both the accuracy and reliability of the forecast? Before looking for the answer, you should understand: why, in fact, should earthquakes be predictable? It is traditionally believed that any phenomenon is predictable if similar events that have already occurred are studied sufficiently fully, in detail and accurately, and forecasting can be built by analogy. But future events take place under conditions that are not identical to the previous ones, and therefore will certainly differ from them in some way. This approach can be effective if, as is implied, the differences in the conditions of the origin and development of the process under study in different places at different times are small and change its result in proportion to the magnitude of such differences, that is, also insignificantly. When such deviations are repeated, random, and have different meanings, they essentially cancel each other out, making it possible to ultimately obtain a not absolutely accurate, but statistically acceptable forecast. However, the possibility of such predictability was called into question at the end of the 20th century.

Pendulum and sand pile

It is known that the behavior of many natural systems is described quite satisfactorily by nonlinear differential equations. But their decisions at a certain critical point in evolution become unstable and ambiguous - the theoretical trajectory of development branches out. One or another of the branches is unpredictably realized under the influence of one of the many small random fluctuations that always occur in any system. It would be possible to predict the choice only with precise knowledge of the initial conditions. But nonlinear systems are very sensitive to their slightest changes. Because of this, choosing a path sequentially at only two or three branching points (bifurcations) leads to the fact that the behavior of solutions to completely deterministic equations turns out to be chaotic. This is expressed - even with a gradual increase in the values ​​of any parameter, for example pressure - in the self-organization of collective irregular, abruptly rearranging movements and deformations of system elements and their aggregations. Such a regime, paradoxically combining determinism and chaos and defined as deterministic chaos, different from complete disorder, is by no means exceptional, and not only in nature. Let's give the simplest examples.

By squeezing a flexible ruler strictly along the longitudinal axis, we will not be able to predict in which direction it will bend. Swinging a frictionless pendulum so much that it reaches the point of the upper, unstable equilibrium position, but no more, we will not be able to predict whether the pendulum will go backwards or make a full revolution. By sending one billiard ball in the direction of another, we approximately predict the trajectory of the latter, but after its collisions with the third, and even more so with the fourth ball, our predictions will turn out to be very inaccurate and unstable. By increasing a pile of sand with a uniform addition, when a certain critical angle of its slope is reached, we will see, along with the rolling of individual grains of sand, unpredictable avalanche-like collapses of spontaneously arising aggregations of grains. This is the deterministic-chaotic behavior of a system in a state of self-organized criticality. The patterns of mechanical behavior of individual sand grains are supplemented here with qualitatively new features determined by the internal connections of the aggregate of sand grains as a system.

In a fundamentally similar way, the discontinuous structure of rock masses is formed - from the initial dispersed microcracking to the growth of individual cracks, then to their interactions and interconnections. The rapid growth of a single, previously unpredictable disturbance among competing ones turns it into a major seismogenic rupture. In this process, each single act of rupture formation causes unpredictable rearrangements of the structure and stress state in the massif.

In the above and other similar examples, neither the final nor intermediate results of the nonlinear evolution determined by the initial conditions are predicted. This is not due to the influence of many factors that are difficult to take into account, not to ignorance of the laws of mechanical motion, but to the inability to estimate the initial conditions absolutely accurately. In these circumstances, even the slightest differences quickly push initially similar developmental trajectories as far apart as desired.

The traditional strategy for predicting disasters comes down to identifying a distinct precursor anomaly, generated, for example, by the concentration of stresses at the ends, kinks, and intersections of discontinuities. To become a reliable sign of an approaching shock, such an anomaly must be single and stand out in contrast against the surrounding background. But the real geoenvironment is structured differently. Under load, it behaves as a rough and self-similar block (fractal). This means that a block of any scale level contains relatively few blocks of smaller sizes, and each of them contains the same number of even smaller ones, etc. In such a structure there cannot be clearly isolated anomalies on a homogeneous background; it contains non-contrasting macro-, meso- and microanomalies.

This makes traditional tactics for solving the problem futile. Monitoring the preparation of seismic disasters simultaneously in several relatively close potential sources of danger reduces the likelihood of missing an event, but at the same time increases the likelihood of a false alarm, since the observed anomalies are not isolated and are not contrasting in the surrounding space. It is possible to foresee the deterministic-chaotic nature of the nonlinear process as a whole, its individual stages, and scenarios for the transition from stage to stage. But the required reliability and accuracy of short-term forecasts of specific events remain unattainable. The long-standing and almost universal belief that any unpredictability is only a consequence of insufficient knowledge and that with a more complete and detailed study, a complex, chaotic picture will certainly be replaced by a simpler one, and the forecast will become reliable, turned out to be an illusion.

It seems that natural disasters happen once every hundred years, and our vacation in one or another exotic country lasts only a few days.

Frequency of earthquakes of different magnitudes in the world per year

• 1 earthquake with a magnitude of 8.0 or higher
• 10 – with a magnitude of 7.0 – 7.9 points
• 100 – with a magnitude of 6.0 – 6.9 points
• 1000 – with a magnitude of 5.0 – 5.9 points

Earthquake intensity scale

Mexico City, Mexico

One of the world's most populous cities is known for its insecurity. In the 20th century, this part of Mexico felt the force of more than forty earthquakes, the magnitude of which exceeded 7 points on the Richter scale. In addition, the soil under the city is saturated with water, which makes high-rise buildings vulnerable in the event of natural disasters.

The most destructive earthquakes occurred in 1985, when about 10,000 people died. In 2012, the epicenter of the earthquake was in the southeastern part of Mexico, but vibrations were well felt in Mexico City and Guatemala, about 200 houses were destroyed.

The years 2013 and 2014 were also marked by high seismic activity in different parts of the country. Despite all this, Mexico City is still attractive to tourists due to its picturesque landscapes and numerous monuments of ancient culture.

Concepcion, Chile

Chile's second largest city, Concepción, located in the heart of the country near Santiago, regularly falls victim to tremors. In 1960, the famous Great Chilean earthquake with the highest magnitude in history, magnitude 9.5, destroyed this popular Chilean resort, as well as Valdivia, Puerto Montt, etc.

In 2010, the epicenter was again located near Concepción, about one and a half thousand houses were destroyed, and in 2013 the source sank to a depth of 10 km off the coast of central Chile (magnitude 6.6 points). However, today Concepcion does not lose popularity among both seismologists and tourists.

Interestingly, the elements have haunted Concepcion for a long time. At the beginning of its history, it was located in Penko, but due to a series of destructive tsunamis in 1570, 1657, 1687, 1730, the city was moved just south of its previous location.

Ambato, Ecuador

Today, Ambato attracts travelers with its mild climate, beautiful landscapes, parks and gardens, and massive fruit and vegetable fairs. Ancient buildings from the colonial era are intricately combined here with new buildings.

Several times this young city, located in central Ecuador, two and a half hours drive from the capital Quito, was destroyed by earthquakes. The most powerful tremors were in 1949, which leveled many buildings and claimed more than 5,000 lives.

Recently, seismic activity in Ecuador has continued: in 2010, an earthquake with a magnitude of 7.2 occurred southeast of the capital and was felt throughout the country; in 2014, the epicenter moved to the Pacific coast of Colombia and Ecuador, however, in these two cases there were no casualties .

Los Angeles, USA

Predicting destructive earthquakes in Southern California is a favorite pastime of geological survey specialists. The fears are fair: the seismic activity in this area is associated with the San Andreas Fault, which runs along the Pacific coast across the state.

History remembers the powerful earthquake of 1906, which claimed 1,500 lives. In 2014, the sun twice survived tremors (magnitude 6.9 and 5.1), which affected the city with minor destruction of houses and severe headaches for residents.

True, no matter how much seismologists frighten with their warnings, the “city of angels” Los Angeles is always full of visitors, and the tourist infrastructure here is incredibly developed.

Tokyo, Japan

It is no coincidence that a Japanese proverb says: “Earthquakes, fires and father are the most terrible punishments.” As you know, Japan is located at the junction of two tectonic layers, the friction of which often causes both small and extremely destructive tremors.

For example, in 2011, the Sendai earthquake and tsunami near the island of Honshu (magnitude 9) led to the death of more than 15,000 Japanese. At the same time, Tokyo residents have already become accustomed to the fact that several minor earthquakes occur every year. Regular fluctuations only impress visitors.

Despite the fact that most buildings in the capital were built taking into account possible shocks, residents are defenseless in the face of powerful disasters.

Repeatedly throughout its history, Tokyo disappeared from the face of the earth and was rebuilt again. The Great Kanto Earthquake of 1923 turned the city into ruins, and 20 years later, rebuilt, it was destroyed by large-scale bombing by American air forces.

Wellington, New Zealand

The capital of New Zealand, Wellington, seems to be created for tourists: it has many cozy parks and squares, miniature bridges and tunnels, architectural monuments and unusual museums. People come here to take part in the grandiose Summer City Program festivals and admire the panoramas that became the film set for the Hollywood trilogy The Lord of the Rings.

Meanwhile, the city was and remains a seismically active zone, experiencing tremors of varying strength from year to year. In 2013, just 60 kilometers away, a magnitude 6.5 earthquake struck, causing power outages in many parts of the country.

In 2014, Wellington residents felt tremors in the northern part of the country (magnitude 6.3).

Cebu, Philippines

Earthquakes in the Philippines are a fairly common occurrence, which, of course, does not frighten those who like to lie on the white sand or snorkel in clear sea water. On average, more than 35 earthquakes with a magnitude of 5.0-5.9 points and one with a magnitude of 6.0-7.9 occur here per year.

Most of them are echoes of vibrations, the epicenters of which are located deep under water, which creates the danger of a tsunami. The 2013 earthquakes claimed more than 200 lives and caused serious damage in one of the most popular resorts in Cebu and other cities (magnitude 7.2).

Employees of the Philippine Institute of Volcanology and Seismology are constantly monitoring this seismic zone, trying to predict future disasters.

Sumatra Island, Indonesia

Indonesia is rightfully considered the most seismically active region in the world. The westernmost one in the archipelago has become especially dangerous in recent years. It is located at the site of a powerful tectonic fault, the so-called “Pacific Ring of Fire.”

The plate that forms the floor of the Indian Ocean is being squeezed under the Asian plate here as quickly as a human fingernail grows. The accumulated tension is released from time to time in the form of tremors.

Medan is the largest city on the island and the third most populous in the country. Two major earthquakes in 2013 seriously injured more than 300 local residents and damaged nearly 4,000 homes.

Tehran, Iran

Scientists have been predicting a catastrophic earthquake in Iran for a long time - the entire country is located in one of the most seismically active zones in the world. For this reason, the capital Tehran, home to more than 8 million people, was repeatedly planned to be moved.

The city is located on the territory of several seismic faults. An earthquake of magnitude 7 would destroy 90% of Tehran, whose buildings are not designed for such violent elements. In 2003, another Iranian city, Bam, was destroyed by a 6.8 magnitude earthquake.

Today Tehran is familiar to tourists as the largest Asian metropolis with many rich museums and majestic palaces. The climate allows you to visit it at any time of the year, which is not typical for all Iranian cities.

Chengdu, China

Chengdu is an ancient city, the center of the southwestern Chinese province of Sichuan. Here they enjoy a comfortable climate, see numerous sights, and become immersed in the unique culture of China. From here they travel along tourist routes to the gorges of the Yangtze River, as well as to Jiuzhaigou, Huanglong and.

Recent events have reduced the number of visitors to the area. In 2013, the province experienced a powerful earthquake with a magnitude of 7.0, when more than 2 million people were affected and about 186 thousand houses were damaged.

Residents of Chengdu annually feel the effects of thousands of tremors of varying strength. In recent years, the western part of China has become especially dangerous in terms of seismic activity of the earth.

What to do in case of an earthquake

• If an earthquake catches you on the street, do not go near the eaves and walls of buildings that may fall. Stay away from dams, river valleys and beaches.
• If an earthquake strikes you in a hotel, open the doors to freely leave the building after the first series of tremors.
• During an earthquake, you should not run outside. Many deaths are caused by falling building debris.
• In case of a possible earthquake, it is worth preparing a backpack with everything you need for several days in advance. A first aid kit, drinking water, canned food, crackers, warm clothes, and washing supplies should be at hand.
• As a rule, in countries where earthquakes are a common occurrence, all local cellular operators have a system for alerting customers about an approaching disaster. While on vacation, be careful and observe the reaction of the local population.
• After the first shock there may be a lull. Therefore, all actions after it must be thoughtful and careful.