How to understand a small epicenter and a large earthquake, and how to understand a small earthquake

Small epicenters, large earthquakes are the concept of earthquake resistance, and each region has a specified fortification intensity in the national seismic fortification division. The seismic code stipulates that the seismic concept of buildings is that small earthquakes are not damaged, medium earthquakes can be repaired, and large earthquakes cannot collapse; A small earthquake is not bad, that is, when it encounters the impact of ** below the fortification intensity of the area, it is generally not damaged or can continue to be used without repair. Medium earthquake repairability is when encountering the impact of the fortification intensity in the area, it may be damaged, and it can still be used after general repair or no repair.

The failure of a major earthquake means that when it encounters the impact of ** higher than the fortification intensity of the region, it will not collapse or cause serious damage that threatens life.

This is a popular name for the degree of intensity, the amount of energy released to divide, the magnitude of the earthquake can be through the instrument.

The higher the magnitude, the more energy is released. The magnitude standard used in China is the international general magnitude standard, called "Richter scale". Grading standards vary from country to country and from region to region.

Generally, ** less than 1 is called ultra-microseismic shock.

If it is greater than or equal to 1 and less than 3, it is called a weak earthquake or a microearthquake.

Greater than or equal to grade 3, less than grade is called sensible**.

Earthquakes greater than or equal to magnitude and less than magnitude 6 are called moderately strong earthquakes.

Earthquakes greater than or equal to magnitude 6 and less than magnitude 7 are called strong earthquakes.

Those greater than or equal to 7 levels are called large**.

Level 8 and above are called huge**.

To date, the largest recorded class in the world was Chile in South America in 1960.

Intensity: Intensity refers to the degree of damage to buildings such as ground and houses. For the same **, different areas, the intensity is different. If it is close to the epicenter, the damage will be great and the intensity will be high; If you are far away from the epicenter, the damage will be small and the intensity will be low.

Less than three degrees: people have no feelings, only instruments can record them;

Three degrees: people feel it in the dead of night;

4-5 degrees: the sleeping person wakes up, the chandelier swings;

Six degrees: utensils tipped, slight damage to the house;

6-7 degrees: house damage, ground cracks;

9-10 degrees: the house collapses, and the ground is seriously damaged;

10-12 degrees: devastating destruction.

Small, medium and large rent-resistant earthquakes are divided according to the level of ground slow earthquakes, as follows:

1.Small earthquakes: Small earthquakes usually refer to earthquakes with a magnitude between **, which are weak and generally have no impact on buildings and man-made structures.

2.Medium earthquake: Medium earthquake usually refers to the magnitude of the earthquake between **, the tremor is strongly felt, and the vibration of buildings and man-made structures can be felt, but generally does not cause significant impact or loss.

3.Major earthquakes: large earthquakes usually refer to earthquakes with a magnitude above **, which are extremely strong, and can cause serious impacts such as the collapse of buildings and man-made structures and landslides, and pose a great threat to the safety of people's lives and property.

In addition, according to the genesis of the wave and the characteristics of the wave, it can also be divided into tectonics, volcanoes, subsidence and induction.

Small earthquakes, including the first magnitude of the earthquake in the whole section, are weak and generally have no impact on buildings and man-made structures. Moderate earthquakes, usually with magnitude between **, are felt strongly and can feel the vibration of buildings and man-made structures, but generally do not cause significant impact or loss. Large earthquakes, wide fronts usually refer to the magnitude of the earthquake above **, the earthquake is extremely strong, can cause the collapse of buildings and man-made structures that burn carefully, landslides and other serious impacts, and pose a great threat to the safety of people's lives and property.

According to the existing scientific level and economic conditions, China has put forward the fortification goal of "three levels" for building earthquake resistance, that is, the commonly said "small earthquakes do not make noise and the manuscript is broken, medium earthquakes can be repaired, and large earthquakes do not collapse".

The usual small, medium and large earthquakes refer to the probability of 50 years beyond 63% (frequent encounters**), 10% (fortification intensity**), 2 3% (rare old ships**).

Small earthquakes"The elastic displacement of the structure and the internal force of the component are calculated, and the cross-section reinforcement is designed by the ultimate limit state method, and the bearing capacity of the cross-section is carried out"Seismic design"，"Deformation design"

And according to the ductility and energy consumption requirements, the corresponding structural measures are adopted.

1.There are generally no small earthquakes before the big **, but there must be aftershocks after the earthquake. 2.

There will be the following situation before the big **, in the period before the earthquake, there will always be some abnormal changes near the earthquake area. For example, the change of groundwater, sudden rise, fall or change taste, turbidity, sound, bubbling. Meteorological changes, such as sudden cold and hot weather, major droughts, floods, changes in electromagnetic fields, abnormal reactions of animals and plants before earthquakes, etc.

**Magnitude is a classification of the amount of energy emitted by the source. The greater the amount of energy released, the greater the magnitude. The magnitude of the earthquake is divided into nine magnitudes, and people who are generally less than the magnitude have no feeling; People above the level have feelings; ** above level 5 will cause damage. Abbreviated as magnitude.

Generally, ** less than 1 is called ultra-microseismic shock.

Greater than or equal to 1, less than 3 is called weak earthquake or microseismic greater than or equal to 3, less than 3 is called felt**.

Earthquakes greater than or equal to magnitude and less than magnitude 6 are called moderately strong earthquakes.

Earthquakes greater than or equal to magnitude 6 and less than magnitude 7 are called strong earthquakes.

Those greater than or equal to 7 levels are called large**.

Level 8 and above are called huge**.

According to the existing scientific level and economic conditions, China has put forward the fortification goal of "three levels" for the earthquake resistance of buildings, that is, the commonly said "small earthquakes are not bad, medium earthquakes can be repaired, and large earthquakes do not collapse".

Usually the small, medium, and large earthquakes refer to the 50-year surpassing probability of 63% (frequent encounter**), 10% (fortification intensity**), and 2 3% (rare encounter**).

Small earthquakes"The elastic displacement of the structure and the internal force of the component are calculated, and the cross-section reinforcement is designed by the ultimate limit state method to carry out the bearing capacity of the cross-section"Seismic design"，"Deformation design"And according to the ductility and energy consumption requirements, the corresponding structural measures are adopted.

Small** does not necessarily occur frequently before the big **. The reason for the occurrence of ** is that the plates on the earth squeeze and collide with each other, resulting in dislocation and rupture on the edge of the plate and the inside of the plate, but the occurrence of the earthquake also needs to have a factor, that is, there must be enough energy, if a place often quarrels with small **, then the energy in the earth's crust will be released frequently, will not accumulate energy, and the remaining energy is insufficient, so it usually does not cause a large **. <

Small** does not necessarily occur frequently before the big **. The reason for the occurrence of ** is that the plates on the earth squeeze and collide with each other, resulting in the edge of the plate and the interior of the plate to produce errors and bumps and burials and ruptures, but the occurrence of ** also needs to have a factor, that is, to have enough energy, if a place often occurs small**, then the energy in the earth's crust will be released frequently, and the energy will not be accumulated, so the remaining energy is insufficient, so usually speaking, it will not cause a large **.

Not necessarily. If it is a small ** alone, there will generally be no big ** behind. But if it is a large group of small **, then it is likely to be foreshock activity, and there may be a large **.

**, also known as ground motion and ground vibration, is a natural phenomenon that produces ** waves during the rapid release of energy in the earth's crust. The squeezing and collision between plates on the earth causes dislocation and rupture on the edge of the plate and the interior of the plate, which is the main reason for the conflict.

**The place where it begins to occur is called the hypocenter, and the ground directly above the epicenter is called the epicenter. The most destructive** ground vibration is called the extreme earthquake zone, and the extreme earthquake zone is often the area where the epicenter is located. It often causes serious casualties, can lead to disasters, floods, toxic gas leaks, the spread of bacteria and radioactive materials, and may also cause secondary disasters such as tsunamis, landslides, collapses, and ground fissures.

You're actually talking about the ** sequence problem. Generally, the large and small events that occur within a certain period of time (days, months or years) before and after a strong earthquake are arranged in time and are called a sequence. According to the proportional relationship of size and energy release characteristics in each sequence, the sequences are divided into three types: mainshock type, earthquake group type and isolated type.

Before and after the occurrence of a strong **, a series of ** often occurs in the epicenter and its vicinity, and this series is called a **sequence by scientists.

In most cases, the one that occurs first is the largest, which is called the mainshock. The smaller ones that follow are called aftershocks. And, in general, the frequency of aftershocks decreases over time, and the magnitude decreases with fluctuations.

There are more earthquake cases accumulated, and after careful research, it is found that there are other situations: the first occurrence of ** is not necessarily the largest. People still call the largest of these series of ** mainshocks, and the ** that occurs before the mainshocks is called foreshocks; There are also cases where the magnitude of the two or several largest earthquakes is about the same.

The magnitude of the mainshock type is high and prominent, and the energy released by the mainshock accounts for more than 90% of the whole ** sequence, which is divided into two categories: "mainshock-aftershock" and "foreshock-mainshock-aftershock"; The biggest feature of the mainshock type is that the magnitude of the mainshock is prominent, and the magnitude difference between the mainshock and the maximum foreshock and the maximum aftershock is significant.

There is no prominent mainshock in the earthquake swarm type, and the main energy is released through multiple ** with similar magnitude; The biggest feature of the earthquake swarm type is that there is no prominent mainshock, and the magnitude of the foreshock, aftershock and mainshock is relatively close, and the difference is generally within 1 magnitude.

Isolated (single**).

Its main feature is that there are almost no foreshocks and almost no aftershocks. The most important feature of the isolated type is that the foreshocks and aftershocks are few and small, and the magnitude of the shock is very different from the mainshock.

The sequence in which the difference between the magnitude of the largest and the second largest is less than or equal to that of the double earthquake type is classified as a double earthquake type. It accounts for about 13% of the total number of ** sequences.

Examples of types. Wenchuan magnitude 8** belongs to the mainshock-aftershock type, and there were rumors in the middle that it was a shock group type, which caused a lot of panic in the society.

**Bureau** can't be, it depends on luck!