Japan Earthquake: How Can Buildings Be More Resilient?

When earthquakes occur, the resulting building collapses, no the tremors themselves, are what lead to high death tolls. How should buildings be constructed to prevent deaths and injuries?The primary cause of death in an earthquake is not the shaking ground but crumbling roofs, crashing walls and collapsing buildings.

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This has been the case historically, even in Japan, where earthquakes are common. At least 48 people have been killed in the most recent tremors in western Japan, and the death toll is expected to rise as the country scrambles to rescue many more injured and trapped under the debris of destroyed homes.

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According to the Japan Meteorological Agency, the strongest of the 21 earthquakes had a magnitude of 7.6.

How do earthquakes cause buildings to collapse?

Earthquakes can cause buildings to stretch, compress or shear.

Shearing occurs when unaligned forces act on different parts of the building, like twisting a sponge. During a quake, these forces can act on a building from side to side and along its length.

While rock and brick walls can handle compression loads very well, they crack and collapse when stretched or exposed to a shear force. Steel is a much more flexible material, which is why it often forms the skeletons of buildings surviving earthquakes.

How can we make buildings resistant to earthquakes?

While earthquakes can't be prevented, buildings can be constructed to minimize deaths and injuries during an earthquake and its aftershocks.

Concrete reinforced with steel in buildings can offer better resilience in contrast to traditional construction materials like sand and gravel, according to Mehrdad Sasani, a civil and environmental engineering professor at Northeastern University in the United States.

Steel, for example, bends considerably before breaking, strengthening larger buildings against quakes. In smaller buildings, bamboo can also be used for this purpose.

Sasani said using a quality-controlled mixture of clay and sand and "adding straw will help control micro-cracks."

Further, having lightweight roofs can go a long way in reducing death from building collapses as people trapped under them suffer fewer and less severe injuries. Wood and metal are better for roofs than heavy materials in earthquake-prone areas, according to a study by Nature magazine.

Since lightweight materials are more flexible, they keep their shapes as they fall during an earthquake.

Quake-resilient innovations

The World Economic Forum has recommended that buildings be fitted with "base isolation" systems to separate the building from its foundations using springs or runners.

"This means that when an earthquake starts, the resulting movement will not impose stress on the structure of the building," the forum said.

Many buildings in Japan and Chile use this technology.

The costs of such constructions are often prohibitively high, so other countries have been looking for simple and cost-effective strategies against quake damages.

Nepal, another country affected by frequent earthquakes, uses one technique of blending affordable materials like straw bales, used tires and plastic bottles into construction.

Elsewhere in Africa, the South African Housing & Infrastructure Fund will implement concrete 3D-printed houses that are both earthquake-resilient and cost-effective.

3D-printed concrete will allow builders more customization, including designing structures that can handle the erratic forces of earthquakes.

Given that building damage is the leading cause of death in an earthquake, implementing smart building engineering will save property and infrastructure from collapse and, most importantly, save lives and prevent injury.

Lessons from Morocco earthquake

On the night of September 8, 2023, a 6.8 magnitude earthquake struck Morocco under the Atlas Mountains, near Marrakech, a popular tourist destination. The devastation the tremor caused brought building resilience to the limelight.

Traditional construction methods used in many parts of Morocco and the old buildings there were not regulated for disaster resilience and cannot handle an earthquake of this scale, according to Sasani, the environmental engineering expert.

A major problem in Morocco was using mud-brick construction and masonry that did not have "reinforcement," he told DW.

Materials like concrete, gravel and mud are preferred in Morocco as they serve as barriers to the scorching heat. These houses are designed with extreme temperature resilience in mind but can't withstand earthquakes very well.

"Due to their rigid construction and limited capacity to absorb the energy of strong ground-shaking, these structures are at risk of collapse," according to the US Resiliency Council, a nonprofit that promotes better design for buildings in earthquake-prone areas.

It added that non-ductile concrete buildings make up most earthquake losses worldwide. Similar problems caused such mortality and injury rates in the Turkey-Syria earthquakes that took place in February 2023.

Editor's note: This has been updated from an older article published on September 13, 2023.

Edited by: Fred Schwaller and Davis VanOpdorp

(The above story first appeared on LatestLY on Jan 03, 2024 04:10 PM IST. For more news and updates on politics, world, sports, entertainment and lifestyle, log on to our website latestly.com).