How Taiwan's tallest building survived the earthquake: Taipei 101 has a 660-tonne pendulum that transfers energy into giant shock absorbers - helping the 1,670ft high skyscraper to sway rather than topple

Taiwan has been hit by its strongest earthquake in 25 years, killing at least nine people, toppling buildings and even triggering tsunami warnings. 

But amid the chaos, eerie footage shows the island's tallest building – the $1.8 billion Taipei 101 skyscraper – gently swaying like a stick in the breeze. 

Measuring 1,671 feet in height, the building is fitted with an ingenious solution that reduces overall building sway by 40 per cent during quakes and winds. 

A 660 metric ton golden sphere called the 'tuned mass damper' hangs inside the building from the 92nd floor. 

As the building moves in one direction, the steel sphere sways in the other direction and maintains the building's overall balance. 

Key to Taipei 101's impressive structural integrity is a 660 metric ton golden sphere that hangs from the 92nd floor 

READ MORE: Huge 7.5 magnitude quake rocks Taiwan

The magnitude-7.4 quake struck just before 8am local time on Wednesday 

If wind or the force of an earthquake pushes the tower to the right, the sphere will provide an immediate and equal force to the left, cancelling out the initial motion. 

So although the tower sways, it doesn't topple. 

It's what's known as a 'passive damping system' meaning it operates without any external power or control – just gravity and the movement of the building. 

Meanwhile, hydraulic pistons underneath the massive sphere absorb and dissipate the energy as heat. 

Dr Agathoklis Giaralis, a professor of structural dynamics at City, University of London, described the clever spherical device as 'like a pendulum'. 

'This steel sphere rests on damping devices which are designed to dampen the relative sway movement between the structure and the sphere, acting in a similar way to the shock absorbers in car suspensions,' he told MailOnline. 

Although it's odd to see a building swaying, modern skyscrapers are built to be flexible, especially in earthquake-prone zones like Taiwan. 

'The materials they are made out of are elastic which means that they stretch or contract according to the changing loads acting on them,' Professor Antony Darby at the University of Bath's Department of Architecture and Civil Engineering told MailOnline. 

'The amount of this deformation in an individual element (e.g. a beam or column) is only very small, but when you multiply this across all the elements in a tall building, this can lead to significant lateral [sideways] movements.

'These movements are not dangerous to the structure itself, but, if excessive can lead to discomfort to occupants.'

Taipei 101 is the tallest building in Taiwan and formerly the tallest building in the world (now the 11th tallest)

Key to the building's amazing structural integrity is a 660 metric ton golden sphere that hangs from the 92nd floor - the 'tuned mass damper'

In Taiwan, Taipei 101 must stand up to earthquakes and typhoons. Every eight floors the building was installed with supporting steel 'outrigger trusses' running from the building's core to its outer columns to increase the towers stiffness, and in order to stop it swaying and vibrating during an earthquake a huge tuned mass damper was installed - a device for transferring energy from the tower's movement into giant shock absorbers. This 660-tonne ball of stacked steel plates hangs on steel cables from the tower's 92nd floor. It's connected to the building's frame through eight fluid-filled shock absorbers

READ MORE: Moment Taiwan is hit by mega earthquake on live TV

Footage shows lights swinging violently from the ceiling 

Construction of Taipei 101 began in 1999 and was completed in time for New Year's Eve 2004, when it finally opened to the public. 

It was designed to resemble a bamboo shoot rising upwards in eight sections – looking like a series of square buckets stacked one on top of the other.

Every floor was installed with supporting steel 'outrigger trusses' running from the building's core to its outer columns to increase the towers stiffness. 

While other tall buildings keep tuned mass dampers hidden, Taipei 101's is visible to visitors on the 88th through 92nd floors, making it something of a tourist attraction.

Unfazed tourists have even filmed the sphere's movement during previous earthquakes, which are a frequent occurrence on the island. 

Taiwan is one country especially prone to earthquakes because it's close to where two tectonic plates meet – the Philippine Sea plate and the Eurasian plate. 

Powerful seismic activity can be detected along the tectonic plate borders, where the plates rub up against each other, causing earthquakes. 

However, Taiwan's earthquake preparedness is 'among the most advanced in the world', according to Stephen Gao, a seismologist and professor at Missouri University of Science and Technology. 

The powerful quake struck off the east coast of Taiwan on Wednesday morning. Taiwan is one country especially prone to earthquakes because it's close to where two tectonic plates meet

This photo taken by Taiwan's Central News Agency (CNA) on April 3, 2024 shows a damaged building in Hualien, after a major earthquake hit Taiwan's east

'The island has implemented strict building codes, a world-class seismological network, and widespread public education campaigns on earthquake safety,' he said.  

As of writing, Taiwan's strongest earthquake in 25 years has killed nine people, while another 50 are missing.

Rescuers expect the total number of injured and killed to rise as the hunt for people trapped by the quake continues. 

The quake and aftershocks also caused 24 landslides and damage to 35 roads, bridges and tunnels, according to government statistics. 

Taiwan's earthquake monitoring agency said the quake was a magnitude of 7.2, while the US Geological Survey (USGS) put it at 7.4. 

The Earth is moving under our feet: Tectonic plates move through the mantle and produce Earthquakes as they scrape against each other

Tectonic plates are composed of Earth's crust and the uppermost portion of the mantle. 

Below is the asthenosphere: the warm, viscous conveyor belt of rock on which tectonic plates ride.

The Earth has fifteen tectonic plates (pictured) that together have moulded the shape of the landscape we see around us today 

Earthquakes typically occur at the boundaries of tectonic plates, where one plate dips below another, thrusts another upward, or where plate edges scrape alongside each other. 

Earthquakes rarely occur in the middle of plates, but they can happen when ancient faults or rifts far below the surface reactivate. 

These areas are relatively weak compared to the surrounding plate, and can easily slip and cause an earthquake.