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How did a 660-tonne steel pendulum protect Taiwan's largest skyscraper during 7.4 earthquake?

Taiwan was struck by its most powerful earthquake in 25 years on Wednesday that killed ten people and injured over 1,000. However, due to its effective disaster response training and laws, the earthquake did fairly minimal damage to life and property.

Edited By: Aveek Banerjee @AveekABanerjee Taipei Published on: April 05, 2024 11:06 IST
Taiwan, earthquake, pendulum, skyscraper
Image Source : REUTERS (FILE) Taiwan's 660-tonne pendulum in Taipei 101 against earthquakes

Taipei: A 7.4-magnitude earthquake struck Taiwan on Wednesday, resulting in the deaths of 10 people and injuring over 1,000 others. This is the most powerful earthquake to strike the island nation since one of magnitude 7.6 in 1999 that killed about 2,400 people and damaged or destroyed 50,000 buildings. As of Friday, authorities are still looking for 18 missing people.

Despite such a powerful earthquake, Taiwan and its capital suffered minimal damage and loss of lives. It is important to mention that Taiwan is one of the most earthquake-resilient countries, despite being prone to such tremors. Consider this - in comparison to Taiwan, a 7.8 magnitude earthquake struck Turkey in early 2023 and killed a staggering 53,000 people.

Since a 2018 earthquake of magnitude 6.4 which claimed seven lives, local authorities have strengthened coordination with government units and non-governmental organisations for disaster response and relief. This time, county officials and police along with other units who helped evacuate residents in affected areas of downtown Hualien city worked together to clear one of the damaged buildings before it could collapse in any aftershocks.

How does a pendulum help in protecting against earthquakes?

In one of the most astounding ways of disaster prevention against earthquakes, Taiwan's largest skyscraper called 'Taiwan 101' has installed a 660-tonne steel pendulum that helped absorb the shock and protected the people inside the building. The "tunnel mass damper" is suspended between several floors of the building and can be viewed by the public.

When the island experiences earthquakes and tsunamis on a regular basis, the sphere moves back and forth to absorb the force of any "violent swinging" and curtails the building's movement by up to 40 percent, the Washington Post reported citing the damper's engineers. This explains why the building was seen hardly moving while other buildings were shaking violently during the earthquake.

The giant pendulum is constructed of 41 layers, each almost 5 inches thick, and is around 18 feet in diameter, according to its website. Ninety-two steel cables are used to hang it, with each being about 3.5 inches wide and 138 feet long, USA Today reports. The sphere also uses a bumper ring to limit its back-and-forth swing to around 59 inches.

This is a rare case in which the engineering is on display, even as several skyscrapers use steel dampers for stability against earthquakes. As part of the passive damping system based on the building's inherent movements, the giant steel ball moves in the opposite direction of the building during a tremor, thus stabilising the structure and not even needing any external energy sources.

Taipei 101 is one of the world's tallest buildings and was at the top until 2009 - at a height of 1,667 feet with 101 stories. The golden mass damper hangs between the 87th and 92nd floors in the centre of the Taipei 101 and can move five feet in any direction.

Why is Taiwan prone to earthquakes?

Taiwan is regularly jolted by quakes and its population is among the best prepared for them, but authorities said they had expected a relatively mild earthquake and accordingly did not send out alerts. The eventual quake was strong enough to scare even people who were used to such shaking. Taiwan is prone to earthquakes because it sits on the Pacific "Ring of Fire" near the junction of two tectonic plates.

More than 100 people were killed in an earthquake in southern Taiwan in 2016, while a 7.3 magnitude quake killed more than 2,000 people in 1999. That caused the government to revise building codes and strengthen disaster management laws. The island country has since staged countrywide disaster drills and mock alert messages for preparations.

The government continually revises the level of quake resistance required of new and existing buildings — which may increase construction costs — and offers subsidies to residents willing to check their buildings' quake resistance. The toll on the high-tech island's 23 million residents has been relatively contained thanks to its excellent earthquake preparedness, experts say.

Taiwanese cities and counties have rescuers on standby 24 hours a day, ready to respond almost at a moment's notice to disasters. Taiwan and its surrounding waters have registered about 2,000 earthquakes with a magnitude of 4.0 or greater since 1980, and more than 100 earthquakes with a magnitude above 5.5, according to the US Geological Survey.

(with inputs from agencies)

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