Characteristics of earthquakes in Chile

On March 17, 2010, in the city of Concepción in central Chile, an office building that was on sale remained standing because of its "strong columns and weak beams" design - although some floors had collapsed Collapse.

At 3 a.m. local time on February 27, a magnitude 8.8 earthquake struck Chile. The intensity of the earthquake shocked the world. Some experts said the Chilean earthquake was as destructive as 100 Haitian earthquakes.

After the catastrophe, Chile and Haiti handed over two completely different disaster reports. The Haitian government estimates that the earthquake killed about 300,000 people—the actual death toll is difficult to accurately estimate.

On March 16, the Chilean government announced a death toll of only 507 (including many victims of the post-earthquake tsunami). This is a catastrophe of the century and an earthquake-resistant miracle.

How did Chile effectively prevent super earthquakes? What lessons can Chile’s experience teach other countries? Our reporter who went to Chile to cover this issue worked hard to find the answer.

Inspiration 1 Earthquake-proof architectural design

One of the reasons why Chile effectively defended against major earthquakes: sophisticated earthquake-resistant design of buildings and strict process supervision

March 10 On the same day, a reporter from Guangzhou Daily took a bus from the airport of Santiago, the capital of Chile, to the city. Traffic was smooth along the way, with traffic speeds exceeding 100 kilometers per hour. Looking around, there is not a single collapsed building visible on both sides of the highway. It is hard to imagine that this is a city that has just experienced a major earthquake.

Although the 8.8-magnitude earthquake occurred 325 kilometers away from Santiago, the earthquake intensity felt by the city of Santiago also reached 8.2.

The earthquake occurred in the early morning while Santiago was still sleeping. When a big earthquake struck, many people were lying in bed one second and fell to the ground the next. What is extremely rare is that this extremely strong shaking lasted for about two and a half minutes.

Legal requirements

All buildings are designed to withstand a magnitude 9 earthquake

After the earthquake, Li Guowei hurried home to check the damage to his house. Li Guowei is a Chilean overseas Chinese originally from Guangzhou. In 2009, he built a villa by himself in the tango town of Carrera, southwest of Santiago.

The scene after opening the door of the house made Li Guowei feel incredible. After experiencing an 8.8-magnitude earthquake and a series of strong aftershocks, the ceramics placed in the house were intact, and there was not a single crack in the entire house.

In fact, 99 houses in San Diego successfully escaped damage after the huge earthquake. Many houses in San Diego suffered cracks, but only more than 20 houses were seriously damaged, leaving 6 million San Diegans unscathed.

Like Li Guowei’s house, all new home construction in Chile has strict construction procedures and supervision processes. The construction process of a new house contains the secret of how many buildings in Chile have successfully withstood major earthquakes.

According to local laws in Chile, all buildings must be designed by professional organizations before construction begins. In early 2009, Li Guowei drew a floor plan of a house according to his own ideas, and then handed it over to a design firm in San Diego for design. "You don't need to worry about earthquakes, designers will consider them."

Li Guowei said that since the 1985 earthquake, the Chilean government has required all buildings to be designed to withstand a magnitude 9 earthquake. In 1985, a magnitude 8 earthquake struck San Diego, killing just over 170 people.

Original: Deliberately "breaking" the floor into two pieces

A month later, the design of the new house was completed. For a simple private house, the design office produced dozens of engineering drawings, covering all aspects of the house structure, water, electricity, gas, etc.

In order to obtain these design drawings, Li Guowei *** paid a design fee of US$20,000 - the design fee is charged based on the construction area. Li Guowei's villa covers an area of ??5,800 square meters and the construction area is 700 square meters.

Subsequently, the design drawings were sent to the San Diego Municipal Public Works Department for review. Only after passing the review can the building permit issued by the government be obtained.

After applying for construction, the government engineering department will charge 1% of the construction cost.

Li Guowei’s villa has a courtyard facing the mountain. Sitting in the yard, Li Guowei proudly introduced the house's unique earthquake-proof design to reporters: "The concrete floor slab is specially designed into two pieces, separated by rubber or foam. When an earthquake strikes, it can buffer the huge impact and ensure that The floor slabs will not break due to twisting. In addition, a lot of reinforcement materials such as steel bars are added to the beams and columns of the house.”

Ingenious earthquake-proof design is one of the unique features of many new buildings in Chile. During the earthquake, one end of a bridge connecting the San Diego airport terminal to the highway collapsed, triggering widespread skepticism. In this regard, the designer's response exceeded everyone's expectations.

It turns out that the designer "designed it this way on purpose." The designer's consideration is that if both ends of the connecting bridge are fixedly connected, when a major earthquake strikes, the strong tension will collapse the terminal building or highway connected to it. Only one end is fixed. When a major earthquake strikes, the unfixed end will naturally collapse after being stressed, protecting both the terminal building and the highway.

The reporter saw in the urban area of ??Concepcion, which was the most severely affected by the Chilean earthquake, a high-rise building with a 30-degree tilt on its head. The floors of several floors collapsed, but the building The column was not broken. Although the floor of a frame structure building collapses, as long as there is no problem with the building's columns, the entire building will not collapse.

Since it is often hit by major earthquakes and knows that the destructive power of major earthquakes is irresistible, the concept of Chilean earthquake-proof design is not to build indestructible buildings, but to buffer and release earthquake energy as much as possible, and maximize Preserve the building as much as possible.

An architectural designer in Santiago said that the earthquake-resistant design of "strong columns and weak beams" is currently widely used in Chile. This design concept is to buffer the seismic energy through the fracture of beams when a major earthquake occurs - but the columns will not break, ensuring that the building will not collapse as a whole as much as possible, thus minimizing casualties.

In addition, it is also one of Chile’s experiences not to build houses that are too high. Except for the capital Santiago, which has some high-rise buildings scattered in the city center, the old city is mostly low-rise buildings. In small and medium-sized cities like Concepcion and Tavaro, most buildings are one or two-story buildings.

Strict supervision: structural engineers, mechanical calculators...

Strict supervision runs throughout the construction process of all new homes in San Diego.

In front of reporters, Li Guowei counted on his fingers: "Once, twice, three times..." During the process of building his house, the structural engineer and mechanical calculator of the design office worked Visited the construction site 7 times.

The first time was before construction started on the house. The construction workers dug several pits more than 1 meter deep in the foundation and surrounding areas. After structural engineers and mechanical calculators checked the soil quality on site, they decided how deep the foundation of the new house should be dug.

The second time was when selecting materials. The types of cement and mild steel used and the thickness of the steel plates must strictly comply with the design standards.

When the foundation was poured, structural engineers and mechanical calculators came again to check the thickness of the steel bars used and the density of the distribution.

Before each concrete pouring, supervisors will take several small boxes of samples and send them to the University of Chile for testing to see if the strength of the concrete meets the design requirements. The Chilean government stipulates that concrete samples must be sent for inspection during the construction of each house.

When it was about to be completed, the designers went to the construction site to conduct a comprehensive inspection, and also carefully checked whether the welding of the metal structure on the roof was firm -

A series of supervision processes were very cumbersome. It takes a long time, but the effect is quite obvious.

It took Li Guowei a full year to build his house. During this period, Li Guowei often went to the construction site, and he "felt very satisfied" when he saw the structural engineers and mechanical calculators supervising the construction site without mercy.

“If you are worried, you can ask a professional from another design firm to supervise the designers of this design firm, but I did not do that.

”

Economical and practical: meticulous design, strict supervision ≠ high housing prices

In addition to reviewing drawings, the Engineering Department of the San Diego Municipal Government is also responsible for acceptance. The acceptance procedure is not complicated , government officials mainly check whether the house is built according to the design drawings, and whether the building structure, shape and various dimensions strictly follow the design data.

Such a sophisticated earthquake-proof design, coupled with such strict process supervision, will make new houses more difficult to build. The economics after completion is also a question that needs to be considered.

The cost of Li Guowei's villa is not too high. The total cost of the villa is 102, which covers an area of ??5,800 square meters and has a construction area of ??700 square meters. Ten thousand US dollars, including US$120,000 for land purchase and US$900,000 for building a house.

A few months ago, a boss from Shunde, Guangdong Province visited San Diego for inspection and was impressed after seeing Li Guowei’s new house: “Same. A house in Shunde costs at least 100 million yuan. ”

In recent years, housing prices in Chile have shown a moderate upward trend, but the increase is much lower than that in large cities in China. Currently, the housing prices of high-rise buildings in the center of Santiago are about 8,000 yuan per square meter.

The Chilean government has a series of subsidy policies for low-income people to buy houses: low-income people purchase houses with a total price of less than 40,000 US dollars, and receive a subsidy of 4,000 US dollars; purchase houses with a total price of more than 40,000 US dollars and less than 80,000 US dollars. , a subsidy of US$8,000; for purchases of houses above US$80,000, there is no subsidy.

At the same time, the Chilean government prohibits foreigners without permanent residency from buying houses locally, which is equivalent to banning international speculators. The attempt was nipped in the bud

Revelation 2: Strong post-event supervision

The second reason why Chile effectively defended against major earthquakes: strong post-event supervision ensured a complete system.

It has been 11 days since the collapse of the Riverbank Building. Monica, a female reporter from Chilean National Television, has also been stationed in front of the building for 11 days. A live news truck parked next to Monica. As soon as there is any new development, she will immediately broadcast live and tell all Chileans

Riverside Building: The only negative example

After the big earthquake, Riverside Building became the first building in Chile. The only high-rise building that collapsed in the center of Concepción, the second largest city, was an outright “toppled building.” The photo of the 50-meter-tall building lying on the ground spread throughout the world and became a phenomenon in Chile. An alternative sign of a major earthquake.

There are less than 1,000 high-rise buildings in Concepción. The catastrophic earthquake caused damage to 57 of them, and 7 of them were seriously damaged. The remaining 50 damaged buildings still need to be demolished or rebuilt.

The reporter saw that most of the framework of the collapsed riverside building was still intact, the columns were broken, and the steel bars were exposed. The head of the building was broken first and tilted 45 degrees to one side. During this period, 52 people escaped from the building. Later, the bottom of the building was also "torn", and the entire building collapsed. Rescued, 8 people unfortunately lost their lives

After the collapse: the family members of the deceased have initiated legal proceedings

In stark contrast to the tragic situation of the Riverbank Building, which is less than 50 meters away. Another high-rise residential building was not greatly affected, but only tilted 20 degrees. The collapsed riverbank building triggered another "earthquake" in Chile.

About. The report on the Riverbank Building has occupied the most important page of the local media for many days. With the media's continuous and inquisitive reporting, all Chileans have focused on this "house that should not have fallen down at all."

After the earthquake, the Chilean government hired U.S. investigators to investigate whether there were quality problems in the building.

The builder of the building was called Sokul Company. After the building collapsed, the company claimed that it had built the building. This building complies with all legal requirements.

Chilean national television reporter Marta said that the family members of the deceased in the Riverbank Building have initiated legal proceedings to sue the construction company and developer respectively. Once the judge confirms that the building does have quality problems, the defendant may be sentenced and face huge fines.

The editor-in-chief of a local Chinese newspaper in Chile said: "Black is black and white is white. Everyone must know the truth." It is precisely because of such an after-action investigation mechanism and strong Supervision by public opinion can ensure that a set of regulations are implemented in place and not reduced to empty talk on paper.

Revelation 3: The "earthquake-proof gene" in the bones

The third reason why Chile effectively defended against major earthquakes: unique geographical conditions and popular earthquake-proof knowledge

Although the magnitude of the Chilean earthquake was higher than that of Haiti, fortunately, its epicenter was located 325 kilometers south of Santiago and 100 kilometers away from Concepcion, with a focal depth of about 35 kilometers. The epicenter of the Haiti earthquake was only 15 kilometers away from the capital, Port-au-Prince, and the focal depth was about 13 kilometers.

Geographical conditions: The vast land is sparsely populated and the epicenter is far away from big cities

The small number of casualties caused by the Chilean earthquake is inseparable from its unique geographical conditions.

Chile is 4,350 kilometers long from north to south, only 362 kilometers at its widest point from east to west, and only 96 kilometers at its narrowest point. It is the narrowest country in the world. The country has a population of 16 million and is sparsely populated.

The capital, Santiago, is the largest city in Chile, with a population of 6 million, and is the only city in the country with a population of over one million; the second largest city, Concepcion, has a population of only 500,000. The reporter traveled more than 2,000 kilometers in Chile, passing through large areas of no-man's land. Sometimes he drove for an hour on the highway without seeing a single house on the roadside.

Such an extremely dispersed population distribution is one of the objective factors why the Chilean earthquake caused fewer casualties.

Taking it for granted: The awareness of earthquake prevention is deeply rooted in the bones

Chilean people generally have earthquake awareness, which is also one of the important factors in the fewer casualties.

Currently, most of the world’s recorded super earthquakes have occurred in Chile. On May 22, 1960, the world's largest earthquake on record occurred in Chile, with a magnitude of 9.5 on the Richter scale. The earthquake triggered three major tsunamis, killing 5,700 people. In 1985, another magnitude 8 earthquake occurred in Chile; this year another magnitude 8.8 earthquake occurred.

According to records, Chile is the country with the most frequent earthquakes in the world, and a quarter of the world's earthquake energy is released from the long and narrow Chile. "Every Chilean knows that a major earthquake will occur every 20 years or so." said Mr. Bao, a Chinese living in Chile.

When talking to people in San Diego, the reporter learned that earthquakes with a magnitude of around 4 "happen frequently" and are "a common occurrence." In their eyes, "these (earthquakes around magnitude 4) are not considered earthquakes."

Due to frequent earthquakes, every Chilean has a natural “anti-earthquake gene”. After the devastating earthquake, Takaballo, the most severely affected port city, performed a miracle: a tsunami was triggered after the earthquake, but no one was injured in a fishing village of 700 people on the coast of Takaballo, and the fishermen's awareness of earthquake prevention was in-depth. marrow.

After the big earthquake, 49-year-old Tacavaro fisherman Pedro took nothing with him. He called his children and ran to a nearby hill. Based on past experience, Pedro knew that after such a large earthquake, a tsunami would follow. Moments before the tsunami hit, the fishermen informed each other and all ran to the mountains.

After the earthquake, because the personnel monitoring the signal of the Chilean Navy did not understand English, they missed the tsunami warning signal reported by the United States. As a result, the Chilean government temporarily canceled the tsunami warning signal after the earthquake. But even in this case, all the fishermen in the village successfully escaped.

This makes Genuolo, the mayor of Tacavaro, happy: "This is mainly due to the residents' good awareness of prevention. For them, earthquakes are nothing new."

Peace of mind: Social order quickly restored

After experiencing a major earthquake, the peaceful mentality of Chileans helped the social order in the disaster area quickly return to normal.

In the city of Concepcion, which was hardest hit by the earthquake, reporters saw that people were calm after the earthquake, and there were no panicked faces on the road. Some citizens also took cameras to take pictures in front of the collapsed ruins.

Opposite the collapsed ruins, a couple was kissing passionately as if nothing had happened.

In the hotel where the reporter stayed, people were surfing the Internet safely next to the cracked walls. In the early hours of the morning, there were aftershocks from time to time, and the bed kept shaking, but none of the residents ran out of the room to take shelter.

Ten days after the earthquake, more tourists went to Easter Island. The Lotte character of the Chilean people was confirmed in the words of a tourist: "Everyone can encounter such a thing as an earthquake. One knows what will happen tomorrow.