Earthquake popular science knowledge materials

Seismological Bureau Earthquake popular science knowledge publicity materials

Earthquakes are a natural phenomenon. More than 5 million earthquakes occur on the earth every year. Only about 50,000 of them can be felt by people. Not all earthquakes can cause damage. Why do earthquakes occur? What types of earthquakes occur? How should we face earthquakes? Below we give you a brief introduction.

Part 1 Basic knowledge of earthquakes

Why do earthquakes occur?

Earthquakes are the result of movement of the earth. As the earth moves, the crust is also constantly moving and changing.

The changes in the movement of the earth gradually accumulate huge energy, exerting a very strong force on underground rocks. When the rocks cannot withstand this force, they will suddenly crack and move.

Earthquakes refer to surface vibrations caused by the release of energy due to dislocation and fracture of rock masses in the earth's crust.

The cracking of rocks produces seismic waves. The seismic waves are transmitted to the surface of the earth, and the ground vibrates. This is an earthquake.

What types of earthquakes occur?

There are three main types of natural earthquakes: volcanic earthquakes, subsidence earthquakes and tectonic earthquakes.

Volcanic earthquakes are ground vibrations caused by volcanic eruptions that cause magma to impact the surface. The impact range of volcanic earthquakes is relatively small and the damage caused is relatively small.

Subsidence earthquakes are ground vibrations caused by subsidence of the formation. For example, the collapse of underground limestone caves or the collapse of mine goafs will cause small-scale ground vibrations. Such earthquakes generally cause little damage.

The earthquakes we usually call are tectonic earthquakes.

Tectonic earthquakes are caused by the dislocation and rupture of rock formations deep underground. This type of earthquake accounts for more than 90% of the global earthquakes. The vibration intensity is high and the impact range is wide, so it poses the greatest threat to human beings.

Earthquakes come in different sizes. The size of an earthquake is expressed in magnitude. The stronger the earthquake, the greater the magnitude. Earthquakes can be divided into the following categories according to their magnitude:

Earthquake magnitudes are divided into weak earthquakes, felt earthquakes, destructive earthquakes, and severe destructive earthquakes.

Weak earthquakes: generally refer to earthquakes below magnitude 3. These earthquakes are usually not felt by people and can only be recorded by instruments.

Felt earthquakes: generally refer to earthquakes above magnitude 3 and below magnitude 5. People can feel these earthquakes, but generally do not cause damage. More than 50,000 earthquakes of magnitude 3 or above occur around the world every year.

Destructive earthquakes: generally refer to earthquakes above magnitude 5 that can cause damage to the surface of the earth and its construction facilities. On average, about 1,000 earthquakes of magnitude 5 or above occur globally every year.

Severely destructive earthquakes: refer to earthquakes with magnitude 7 or above. There are 10 to 20 such earthquakes in the world every year, but most of them occur in oceans and desolate places.

For every one level difference in magnitude, their energy differs by more than 30 times. In other words, a magnitude 7 earthquake is equivalent to the power generated by nearly 1,000 magnitude 5 earthquakes.

When an earthquake occurs, seismic waves are generated, and the vibrations people feel are caused by the propagation of seismic waves.

During an earthquake, you often feel up and down first, and then swaying from side to side. This is caused by the characteristics of seismic waves. Seismic waves are mainly composed of longitudinal waves and transverse waves. Longitudinal waves propagate quickly but are relatively weak, making people feel bumpy. Transverse waves propagate slightly slower, but are relatively strong and can cause huge shaking and cause serious damage to surface buildings.

The degree of earthquake damage is not only related to the magnitude of the earthquake, but also related to the source depth, epicenter distance, seismic wave propagation and other factors. We measure the extent of earthquake damage as intensity. Generally speaking, after an earthquake occurs, the epicenter has the most severe damage and the highest intensity. Spreading from the epicenter to the surrounding areas, the intensity gradually decreased. An earthquake has only one magnitude, but can be divided into different intensity zones.

During an earthquake, the place inside the earth where the earthquake occurs is called the source. The point on the ground facing the source of the earthquake is called the epicenter. The distance from the earthquake source to the epicenter is called the focal depth. The distance from any point on the ground to the epicenter is called the epicentral distance.

The distribution of earthquakes on the earth is not uniform. It can be seen from the world epicenter distribution map that the global earthquake distribution has a certain regularity. It is mainly distributed in the Pacific Rim seismic zone, the Eurasian seismic zone and Hailing seismic zone.

China is located in the southeast of Eurasia and faces the Pacific Ocean to the east. It is a country prone to severe earthquake disasters.

From the distribution map of my country's main earthquake zones, we can know that my country's earthquakes are widely distributed, and there are about 20 major earthquake zones across the country.

Part 2: Earthquake Macro Precursor Phenomenon

The phenomena that occur in nature before an earthquake and are related to earthquake gestation are called earthquake precursors. Earthquake precursor anomalies include microscopic anomalies and macroscopic anomalies.

Microscopic anomalies, such as terrain deformation, geomagnetic anomalies, etc., are mainly detected by high-precision scientific instruments.

Macroscopic anomalies refer to abnormalities that can be felt by people’s senses, mainly including groundwater anomalies, animal and plant anomalies, ground sound, ground light and other anomalies.

Changes in well water

There is a way for well water to rise and fall abnormally during drought

Without rain, it becomes muddy, discolored, smelly and smells bad

The jets sound again, and the flowers turn over and bubbles appear.

This is a macroscopic precursor phenomenon of well water in groundwater.

When groundwater bubbles, becomes turbid, has a peculiar smell, etc., it may be an abnormal reaction before an earthquake. Of course, many reasons can cause abnormalities in groundwater, and groundwater may also be affected by other environmental changes.

2. Animal abnormalities

Before many major earthquakes in history, many animals showed "abnormal behaviors" to varying degrees. Therefore, ordinary people call animals "living instruments" for observing earthquake precursors.

The common people made these anomalies into proverbs:

If the mules, horses, oxen and donkeys do not enter the pen, they break free from the reins and run away

The pigs do not eat, the dogs bark, and the rabbits stand up The ears are jumping again and again

Ducks can't get out of the water, chickens can climb trees, pigeons can't fly back to their nests

Hibernating snakes have come out of their holes early, and mice are running all over the streets in groups

Loaches and locusts scurry up and down, fish float to the surface and swirl again

Clearflies fly away in groups, bees startle their nests and sting people and animals

There are many factors that cause animals to become abnormal, so animals have Abnormal behavior is not necessarily a precursor to an earthquake.

3. Ground light and ground sound

Ground light refers to the phenomenon of light in the sky that people see during a major earthquake. In addition to blue and white, the color of ground light also has other colors. Under normal circumstances, small earthquakes are not likely to cause the ground glow phenomenon. The arrival of the ground glow often indicates that a major earthquake will occur soon. Before the 1975 Haicheng, Liaoning, my country, and the 1976 Tangshan, Hebei earthquakes, the ground glow phenomenon was very prominent. If some shock-absorbing measures can be taken quickly and decisively at this time, it is possible to avoid earthquake disasters.

Minutes or hours before an earthquake, there are often sounds coming from deep underground, which people call "earth sounds." According to a survey, 95% of the residents who were awake before the Tangshan earthquake heard the sound of the earth. These sounds are relatively low, rising and falling, completely different from the usual city noise.

Part 3: Identify and eliminate earthquake rumors

Due to the huge disaster of earthquakes, it is easy for people to panic about earthquakes. At this time, earthquake rumors appeared and quickly spread Spread the word. Earthquake rumors are very harmful. They may not only disrupt our study, production and life, but also disrupt social stability and order.

How to identify earthquake rumors?

Rumors often have the following characteristics:

1. The "forecast" earthquake magnitude is very large, and the earthquake time and earthquake are very specific, such as "such and such city", "what day of the month" There will be an earthquake on "Day".

2. Say that a foreigner, an expert or an earthquake agency made a forecast.

3. Forecasts with feudal superstition or accompanied by bizarre legends.

The reason why there is a market for earthquake rumors is that earthquake prediction is a worldwide scientific problem and is still in the exploratory stage.

my country's earthquake forecasting is at the world's leading level, and earthquakes such as Haicheng, Liaoning, etc. have been successfully predicted. But at present, we can only predict certain types of earthquakes to a certain extent, and we cannot predict all earthquakes. In particular, earthquake forecasts are far from as accurate as weather forecasts.

The authority to issue earthquake forecasts in my country lies with the government, and no other unit or individual has the right to issue earthquake forecast information. Article 16 of the Law of the People's Republic of China on Earthquake Prevention and Disaster Mitigation stipulates: The state implements a unified release system for earthquake forecasts.

Therefore, when earthquake news comes, there are thousands of them, but you must remember the most basic one; for earthquake forecast information, only listen to the government.

When dealing with earthquake rumors, we must "do not believe them, do not spread them, and report them promptly."

Part 4: What to do when an earthquake comes

We all know that earthquakes, like wind, rain, thunder and lightning, are a natural phenomenon and an objective law. With the advancement of science and technology, people's methods of preventing and responding to earthquake disasters are also constantly improving.

What should we do once we encounter an earthquake?

First of all, don’t panic or act blindly. Determine whether an earthquake is large or small, near or far based on your feelings. Generally speaking, near earthquakes shake up and down first, and then shake left and right, while distant earthquakes only shake front, back, left, and right. If it is a small earthquake or a distant earthquake, the houses we live in now are basically earthquake-resistant, so there is no need to panic.

Secondly, we must adopt correct methods to avoid earthquakes.

In different places, the methods of avoiding earthquakes are different. Let’s talk about how to avoid earthquakes in schools, homes and public places.

How to avoid shocks at school:

Safety tips: 1. Follow the teacher’s instructions in all actions;

2. Students should take care of each other. Take care of the younger students;

3. Avoid shocks under the desks, evacuate in an orderly manner, and never crowd.

Suppose we are in the classroom and an earthquake suddenly occurs. What should we do?

First of all, we must lie low and wait, squat or sit down, hide our heads under the desk or next to the podium, and never run around. Curl your body as much as possible and lower your center of gravity. Hold on to a sturdy object such as a table leg. Protect your head, neck, eyes, and cover your mouth and nose.

After the earthquake stops, you should immediately evacuate in an orderly manner under the command of the teacher. When evacuating, put your schoolbag on your head and keep a certain distance between the students in front and behind. Especially in narrow places such as classroom entrances and stairwells, you must slow down, help each other if you find students who have fallen, and notify the students behind you in time to avoid crowding.

After running outdoors, be sure to hide in an open and open place as much as possible, with no easy-to-fall objects around or above your head.

If we are in the playground or outdoors, we can squat down without moving, protect our heads with our hands, and be careful to avoid tall buildings or dangerous objects. Never go back to class because you forgot something.

How to avoid shocks at home:

Safety tips: 1. Hide first and then run, don’t run first;

2. Hide in a solid place (under the bed, in a room A small place with support;)

3. If you have time, open the door first and turn off the gas, power, etc.

When avoiding earthquakes, you should take shelter as close as possible according to your position during the earthquake, and then evacuate to a safe place after the shaking stops. Hide under or next to objects that are strong, difficult to tip over, and can protect your body, such as tables, beds, etc. You can also quickly run to a room with smaller openings and support, such as the kitchen, bathroom, etc.

If you have time, open the door first to ensure that the passage is clear; turn off the gas switch and electric gate.

When absorbing shock, climb down to minimize the center of gravity of the body, face down, do not press your mouth and nose, and hold on to solid objects around you. You can also squat or sit down and curl your body as much as possible. Pay attention to protecting the head and neck. Cover the head and back of the neck with your hands. If possible, put an object around you on your head and close your eyes to prevent injury from foreign objects.

3. How to avoid shocks in public places:

Safety tips: 1. Follow the instructions of the staff

2. Don’t rush to the exit. Keep a distance from the person in front of you;

3. If you encounter a crowd, unbutton your collar and cross your hands across your chest to protect your chest.

After a major earthquake, if there is an emergency evacuation site nearby, you should rush to the evacuation site under the guidance of an adult.

Earthquake emergency shelters are generally built in parks, green spaces, playgrounds, and squares, and have basic emergency response functions. For example, emergency command, emergency material distribution, emergency shelters, emergency toilets, etc.

After an earthquake, you should also pay attention to the following issues:

Do not rush to the stairs, as this may cause crowding.

Do not light lights casually, as there may be flammable and explosive gases in the air.

Do not rush to make a call to avoid congested lines and affecting disaster relief command communications.

Part 5: Self-rescue and mutual rescue in earthquakes

When a disaster strikes, we must not only master the basic knowledge of disasters, but also understand the basic skills of self-rescue and understand the principles of self-rescue and mutual rescue. basic measures. According to statistics, during the Tangshan earthquake, 570,000 people were buried and about 450,000 people escaped through self-rescue and mutual rescue. Generally speaking, the survival rate of buried people rescued within half an hour after a major earthquake is 99%. It can be seen that self-rescue is one of the main measures to reduce casualties. Let’s briefly learn about self-rescue and mutual rescue:

1. Self-rescue:

It requires the trapped people to have a firm will Survive perseverance and eliminate fear.

(2) When you cannot escape, you should try to free your hands and feet and cover your mouth and nose to prevent suffocation from smoke and dust.

(3) Keep a clear mind, do not shout for help, use stones or iron tools to hit objects to communicate with the outside world and save your physical strength.

In the Tangshan earthquake, many children and teenagers were buried under pressure, but with their wisdom and tenacious will, they persisted, stayed calm in the face of danger, turned danger into safety, and were eventually rescued and saved their lives.

2. Mutual rescue

The main methods of rescuing people are:

Those who are buried under pressure during excavation should maintain supports to prevent further collapse and injury;

Expose the injured person's head first, remove foreign objects in his mouth and nose, and keep his breathing smooth. If he is suffocated, perform artificial respiration immediately;

If the person who is pressed cannot climb out on his own, Do not pull or pull forcefully to avoid further injuries; patients with spinal injuries should use door panels or hard stretchers when transporting them;

When a survivor who cannot be rescued is found, a mark should be set up for rescue.