If the earthquake occurs under the feet ...

Little friends, when the earthquake happens at your feet, are you afraid of it?

If the earthquake happens to happen at the foot of the city, are you afraid of it?

Such earthquakes have a special name- "Urban Lower -type Earthquake".

What is this "straight down earthquake"?

The development of activity in urban areas is called a straight down -type activity fault. The earthquake that occurs under the city is called the "urban direct earthquake". If the sudden misalignment of the activity faults below the city causes a straight down earthquake, this type of earthquake can directly threaten the city, and the casualties, damage, and economic losses caused by it will greatly exceed the peripheral earthquake of the city. Impact.

Everyone imagines how serious the destruction is if there is an earthquake under the foot of a city! There are many urban buildings and dense population. Once the earthquake occurs, it may cause extremely huge catastrophic consequences. It's terrible to think about it!

How much damage will the "straight down earthquake in the city" cause?

How big destruction? You know a few typical examples.

Everyone has heard of the Tangshan earthquake, this big earthquake belongs to the "urban direct earthquake". At 03:42 on July 28, 1976, a large earthquake with a magnitude 7.8 level occurred in Tangshan and Fengnan, Hebei Province, my country. After the earthquake, the entire Tangshan urban area was razed with flat land. The city's transportation, communications, water supply, and power supply were interrupted. A heavy industrial city was destroyed. The earthquake caused about 240,000 people, and about 160,000 serious injuries. 96%of the buildings and structures were destroyed. 6.3 million civilian houses collapsed, and the direct economic loss was about 10 billion yuan.

1976 Tangshan magnitude 7.8 earthquake

On April 18, 1906, a magnitude 8.3 earthquake occurred in San Francisco. The earthquake not only caused the house to collapse, but also caused a fire, and the fire burned for three days and three nights. In addition to San Francisco, the surrounding cities are also strongly damaged by the earthquake. The earthquake caused more than 700 people to be killed and injured by 250,000 people.

1906 San Francisco 8.3 earthquake

On September 1, 1923, the earthquake occurred in the Kanto earthquake in Yokohama in Japan and the Kanto earthquake in Tokyo. The fire besieged and died. Japan summarized the painful lessons of the Kanto Earthquake, and promulgated the Basic Law of Disaster Countermeasures in 1961, and set September 1st as a national "disaster prevention day" each year.

Glass 7.9 earthquake in Kanto, Japan in 1923

Why does the "urban straight down earthquake" cause such a great destruction?

First of all, the seismic magnitude, the depth of the earthquake, the seismic position, and the characteristics of other earthquake sources are all related to the loss of the disaster. The epicenter distance of the "straight down earthquake" has almost reached the smallest, so it has great destructive power to the city.

Secondly, the destruction of urban buildings is closely related to poor foundation. The terrain, landform, rock layer distribution and mechanics of the site have a direct impact on the earthquake response and building damage of the site. For example, on January 17, 1995, a magnitude 7.3 earthquake in Kobe in Japan also belongs to the "cities straight -down earthquake". Because most buildings of Kobe are built on the soft sedimentary floor and artificially returned to the ground. The severe liquefaction and sinking foundation caused a large number of buildings.

1995 Kobe 7.3 earthquake

Furthermore, with the acceleration of urbanization, the scale of cities has continued to expand and the population is growing, resulting in a "cities' straight down earthquake" can cause a greater degree of economic losses and casualties.

Crowded city

In addition, there are many sources of secondary disasters in cities. In addition to the damage to the building, the earthquake will also cause fire, flood, power outage, water parking, traffic paralysis, and destruction of ground, underground pipelines and lines in the city, especially the arteries and nerves of the city -the destruction of the lifeline engineering, the lifeline project, and the destruction Out of control will cause the loss of urban function to be paralyzed, thereby increasing the loss of earthquake disasters.

In the face of such serious problems, how should we deal with it?

With the development of the economy, the scale of cities has continued to expand, the population and wealth are highly aggregated, and the disaster loss caused by the cities' direct earthquakes is becoming more and more serious, making us pay more attention to the importance of urban earthquake prevention and disaster reduction. By actively carrying out the detection of urban activity faults, it is found that there are activity faults within the scope of the city, the positioning and activity of the activity fault, and evaluating the danger of the earthquake, formulating corresponding countermeasures, and strengthening the earthquake anti -seismic prevention management on this basis. , Improve the anti -seismic standards, strengthen the awareness of earthquake anti -disaster reduction, and establish an emergency response plan for public safety incidents.

At present, my country's urban activity fault detection work is continuously promoted. Dozens of cities have completed urban activity fault detection work, providing scientific basis and technology for major engineering site selection, urban scientific avoidance activity faults, and prediction of large earthquake risk predictions, etc. For reference, this will play a pivotal role in my country's earthquake prevention and disaster reduction work.

references

1. Xiao Heping.

2. Deng Qidong.

3. Yao Lan.

Source: Zhenzhi Zhuojian

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