More than 600 miles, the central earthquake of Friday in Myanmar, the spacious metropolis gathered in the silhouette and swinging Bangkok’s skyscrapers separated from the skyscrapers. 33 -storey high -storey collapsed under construction. How could the tremor in the Thai capital Bangkok be connected to such a remote earthquake?
The answer includes low -frequency seismic waves that can travel large distances and allow high -rise buildings to fall.
When a large earthquake hits, it emits different trembling frequencies at the same time. Some produce quickly back and forth, others produce low -frequency swing.
This was true on Friday, when the earthquake in Myanmar produced violent, high -frequency seismic waves; They destroyed low buildings, Buddhist Pagodes and other structures, close to the earthquake center just outside Mandalay, the second largest city of Myanmar. Most of the destroyed places were made with bricks and walls, with fragile materials sensitive to such shaking.
When released from an earthquake, high -frequency seismic waves spread to the inner part of the world they dispersed. Low -frequency waves move in the world crust and more distance.
According to NASA, during the Earthquake of 7.9 in Alaska in 2002, the low frequency waves traveled so much that according to NASA, the water in the swimming pools and pools caused them to splash away from Texas and Louisian.
Such seismic waves also have special resonance with high buildings.
Similar to the settings that produce different sounds depending on their size, buildings react differently to earthquakes, depending on their designs and especially their heights.
A 10 -storey building may require one second and side by side during an earthquake, while a 50 -storey building may take five seconds for the completion of the same movement, and a nausea can be back and forth.
Low -frequency seismic waves were an important factor in an earthquake in which nearly 900 buildings in Mexico City collapsed in 1985, partially or completely collapsed. Comprehensive destruction was initially astonishing seismologists and engineers, because the 8.0 -magnitude earthquake was a relatively long distance from the city’s central base, where the city was at a distance of 200 miles more than 200 miles.
They concluded that seismic waves entered the resonance with a certain force through the city’s clay and silt soils, a aggravating factor in and after the earthquake.
A similar dynamic had played last Friday. The low -frequency rocking mainland was strengthened in and around the Thai capital when he threw a pulse in Southeast Asia, because the city was built on the soft soils of the Chao Phraya River Delta.
In recent years, scientists say that these soft soils underestimate the potential of making earthquakes more dangerous. Engineers compare dynamics to building a building on Jell-O.
In addition to Bangkok and Mexico City, Los Angeles, San Francisco, Seattle and Tokyo city center, they are cities that can proliferate the destructive power of earthquakes, especially at low frequencies.
In Mexico City in 1985, the frequencies of seismic waves were very important to understand the damage caused by the earthquake. A team of American scientists report In 1987 by the Ministry of Commerce, most of the serious damage was “limited to buildings in the range of seven to 18 floors”. This is because it was a combination of low -frequency seismic waves reaching the city and the vulnerable construction at these frequencies.
“He performed well in general, such as older, low -storey wall buildings, large stone wall colonial churches and government offices.” Paradoxically, these are the types of building that engineers think they are the most vulnerable to trembling near the earthquake central base.
Until the 1950s, many American engineers have prevented the construction of high -rise buildings in earthquake -prone areas, according to Emeritus professor of Emeritus, Professor of the California Institute of California Technology, who spent his five -year career on the buildings.
Judge wisdom, stronger, harder buildings, he said. However, this has changed for decades and today’s skyscrapers are more flexible.
Dr. Heaton says the flexible design of modern skyscrapers works well with around 6 more magnitude earthquakes. However, less frequently emphasizing the fragility of high buildings is very worried about the consequences of larger earthquakes. This staff contains an earthquake of 7.8 magnitude that killed more than 50,000 people in Türkiye two years ago.
Dr. Heaton says a great fault rupture under a modern city – a direct stroke – a direct stroke, no matter what engineering measures, he will be destructive for long buildings.
The severe movement of the ground in failure, cream As seismologists said, he said that a high increase would cause the base of the base to change rapidly and that he would potentially leave without supporting the upper floors.
“When you take the base of a building and move it in a few meters less time, there is almost nothing that a structural engineer can do to keep a building upright,” he said. “I certainly don’t want to be in a really long building during a big earthquake.”
