What caused it and why did a building in Bangkok collapse?

An important earthquake in Myanmar on Friday has caused more than 1,000 deaths and caused the collapse of numerous structures.

Although Myanmar is a high -risk region for earthquakes, damage to buildings has been widespread.

On the other hand, Bangkok is not considered prone to earthquakes. The Thai capital is more than 1,000 km (621 miles) from the epicenter of the earthquake on Friday, and yet, however, an unfinished building of great height in the city was carved by it.

Here we will explain what this earthquake caused and how he could have such a powerful effect so far.

The upper layer of the earth is divided into different sections, called tectonic plates, which move constantly. Some move next to each other, while others are above and below the other.

It is this movement that causes earthquakes and volcanoes.

Myanmar is considered to be one of the most geologically “active” areas of the world because it is located at the top of the convergence of four of these tectonic plaques: the Euroasy Plate, the Indian plaque, the Sunday plate and the Burma microplata.

The Himalayas were formed by the Indian plaque that collided with the Eurasian plaque, and the 2004 tsunami as a result of the Indian plaque that moves under the microplata of Burma.

Dr. Rebecca Bell, a tectonic reader at Imperial College London, said that to accommodate all this movement, failures – cracks in the rock – form that allow tectonic plates to “slide” sideways.

There is an important failure called Sagaing Falla, which cuts through Myanmar, from north to south and has more than 1,200 km (746 miles) long.

The first data suggest that the movement that caused the earthquake of magnitude 7.7 on Friday was a “slip”, where two blocks move horizontally with each other.

This is aligned with the typical saga fault movement.

As the plates move with each other, they can be stuck, building friction until suddenly releases and the earth changes, causing an earthquake.

The earthquakes can occur up to 700 km (435 miles) under the surface. This was only 10 km from the surface, which made it very shallow. This increases the amount of surface agitation.

The earthquake was also very large, measuring 7.7 on the scale. It produced more energy than the atomic bomb fell in Hiroshima, according to the United States geological service.

The size of the earthquake was due to the type of fault, said Dr. Bell.

“The straight nature (of the fault) means that earthquakes can break over large areas, and the larger the area of ​​the failure that slides, the larger the earthquake,” he explained.

“There have been six earthquakes of magnitude 7 or more in this region in the last century.”

This straight failure also means that much of the energy can be transported by its length, which extends by 1200 km south to Thailand.

How earthquakes feel on the surface is also determined by the type of soil.

In the soft soil, which is what Bangkok is built, the seismic waves (the vibrations of the Earth) slow down and accumulate, increasing in size.

Then, Bangkok’s geology would have caused the land to tremble more intense.

While dramatic images have emerged from high -rise buildings in Bangkok swinging during the earthquake – Hitting water on the roof – The unfinished headquarters for the Office of the General Auditor, the Chatuhak district of Bangkok, seems to be the only skyscraper to collapse.

Before 2009, Bangkok did not have a comprehensive security standard to build buildings to resist earthquakes, according to Dr. Christian Málaga-Chuquitaype, Professor of Earthquake Engineering at Imperial College London.

This means that older buildings would have been particularly vulnerable.

This is not unusual, since earthquake -resistant buildings may be more expensive to build and Thailand, unlike Myanmar, it does not frequently experience earthquakes.

Dr. Emily So, professor of architectural engineering at the University of Cambridge, said that older buildings can and have been strengthened, as in California, western Canada and New Zealand.

However, the building that collapsed was new, in fact, it was still under construction when the earthquake hit, and the updated building standards would have applied.

But after having studied the video, Dr. Málaga-Chuquitaype said that it seems that a “flat slab” construction process was being favor, which is no longer recommended in the areas prone to earthquakes.

“A ‘flat slab’ system is a way of building buildings where the floors are made to rest directly in columns, without using beams,” he explained.

“Imagine a table supported only by legs, without extra horizontal supports.

“While this design has architectural costs and advantages, it works badly during earthquakes, often failing in a fragile and sudden way (almost explosive).”

Mandalay in Myanmar was much closer to where the ground slid and would have experienced significantly more severe tremors than Bangkok.

Although Myanmar regularly experiences earthquakes, Dr. Ian Watkinson, professor in Earth Sciences at the Royal Holloway University, thought it was unlikely that many buildings were built to be earthquake proof.

“General poverty, great political agitation, along with other disasters, for example, the Tsunami of the Indian Ocean in 2004, has distracted the country to concentrate on the unpredictable risks of earthquakes,” he said.

“This means that, in many cases, the building design codes do not apply, and construction occurs in areas that could be prone to a higher seismic risk, for example, flood plains and pronounced slopes.”

Parts of Mandalay and its buildings are also found along the flood plain of the River SIVERERWADDY. This makes them very vulnerable to a process called liquefaction.

This happens when the soil has a high water content, and the tremor makes the sediment lose its strength and behave like a liquid. This increases the risk of landslides and construction collapses, since the ground can no longer hold them.

Dr. warned that there was always “a possibility” of additional damage to buildings near a failure line due to replicas, the tremors that follow an earthquake, which can be caused by the sudden transfer of energy to the nearby rock.

“Most of the time replicas are smaller than the main clash, and tend to decrease in size and frequency over time,” he said.

Additional Vicky Wong reports