Buildings weigh a tonne

When one looks at skyscrapers, their weight is something that never comes to mind. Unless of course you are a structural engineer. Then, that’s the only thing you are concerned about.

Buildings, in actual weight terms, weigh a lot. If you calculate the weight of all the steel, concrete, glass, brick, and everything else that goes into the making of a building, and add that you come up with a huge number. In the larger scheme of things, this number is not very high, but if scientists are to be believed, at least one tall skyscraper in Taiwan, may have triggered off some earthquakes. [ hat tip Sakshi ]

According to the geologist Cheng Horng Lin, from the National Taiwan Normal University, the stress from the skyscraper may have reopened an ancient earthquake fault. If he is right, then it raises concerns about proposals such as Sky City 1000 in Japan, the vertical city that has been proposed to solve Tokyo’s housing problems. And it is not just skyscrapers that are a problem. Dams and underground waste deposits may also cause rumblings if they become too large.

On preliminary investigations, the weight of the building in question, TAIPEI 101, is about 700,000 tonnes. That may seem a lot, but then its nothing when compared to dams, and other underground waste dumps. This is not the first time that large man made structures have been blamed for causing tremors and earthquakes. I remember my parents and grandparents always talking about the Koyna Dam and the earthquakes in 1967.

One of the most convincing examples is the Koyna Dam earthquake, which occurred in 1967. More than 120 people died and many more were injured when a magnitude 6.5 earthquake shook the ground around the recently constructed dam in Maharashtra state, India.

I have a personal experience of this phenomenon too. About 10 kms away from our farm near Bulsar, Gujarat is the Kelia Dam. When the dam was built and the resorvoir was flooded, small and large tremors started happening all around the dam for a radius of 25 km. This was in the mid 80’s and everyone in the surrounding villages did not know what to make of it. The Geological Survey of India, set up a monitor station and that recorded earthquake activity on a seismograph 24/7/365. In the subsequent years there was a partial drought and the water levels in the reservoir went down and the earthquakes stopped.

Coming back to buildings and to TAIPEI 101, there is no conclusive proof that the building may be the reason for the new activity in the region.

Zygmunt Lubkowski, an earthquake analyst for the engineering firm Arup, is concerned at the lack of data. “Earthquakes occur on timescales of thousands to millions of years. From just 10 years of earthquake data it is hard to tell if the extra earthquakes are just noise in the signal or due to the building.”

On the one hand, yes the building exerts a weight of 700,000 tonnes on a footprint of about 30 acres but then on the other hand…..

Compared with dams and underground waste deposits, skyscrapers such as Taipei 101 are mere pinpricks on the Earth’s surface. “It is a point load which is probably going to be insignificant at depth,” says Dr Seeber.

Related post: World’s Skyscrapers “Made in India”

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