For those of you, like me, who had no idea what Taipei 101 is, it is the new tallest building in the world. Completed in 2004, it stands over 508 meters (1667 ft) tall. Recently, an increase in microtremors in Taipei has had people asking if this new massive building might be to blame. The theory is, apparently, that some ancient fault has been reopened beneath the building because it is so heavy. From the article, “If a fault is about to crack, then a little pressure can trigger an earthquake. It’s like the last straw that breaks the camel’s back.” I’m more than a little skeptical of this, and my gut reaction was that though the building might seem big to us, the Earth laughs at the such trivial extra weight.
Let me put on my engineer’s hat for just a minute. The building weighs 700,000 metric tons, and stands on a base of approximately 3.5 acres. This translates to a pressure of approximately 4.7 bar at its base, or approximately 4.7 times normal atmospheric pressure. Assuming, conservatively, a density of sediment and rock beneath the tower of 1.5 grams/cm3 (I know, lots of mixed up units, sorry!), 4.7 bar of pressure is equivalent to only 32 meters (105 ft) of sediment. It is likely that the building has a basement at least 30-50 feet deep anyway (just guesswork here), so the effective additional pressure due to the building’s weight is only about 2-3 bar, or somewhere around a trivial extra 55-75 feet of dirt! So, saying that the building is causing the earthquakes seems on its face completely ridiculous considering that slag piles, coal piles, excavation piles, landfills, and all other sorts of additional human-emplaced masses exert more pressure than 2-3 bar.
It is, of course, not impossible that such a slight additional pressure load could trigger some fault, the whole “straw that broke the camel’s back” idea. But, until a bit more study has been done on the exact mechanism at work here, let’s not start abandoning plans for bigger and heavier skyscrapers, like Tokyo’s proposed Sky City 1000. In the meantime, the media needs to ask a few tougher questions before so broadly publicizing a theory that is more likely (at least at first blush) to be incorrect than otherwise.
I hadn’t heard that, it’s pretty funny. I go to Taiwan a lot and I’ve been to the top of Taipei 101 and saw the engineering presentation and the 800 ton tuned-mass damper system that was built at the bottom and raised to the 89th floor as the floors were constructed. Aside from your plausible back-of-the-envelope pressure calculation, this building received some SERIOUS earthquake engineering by Japanese companies specializing in this. They didn’t just slap this baby up and hope for the best.
I’ll check with my Taiwan contacts on what the local spin is from rational people.
-Bruce
I had heard this earlier and thought “whatever.” You are right that the media has a tendency to overhype and react to anything that will sell papers and advertising. (Hurricane Katrina anyone?) Your enginnering calculation seems sound. Does the 700,000 metric ton weight include the stuff inside the building? I remember rumors at MSU that the engineering library was sinking because they forgot to account for the weight of the books.
Not sure if the weight of the stuff inside the building was included in that weight. Honestly, the tonnage came from the CNN story and a Wikipedia entry (both agreed), so I am not super confident in those, but I would have to be off by a pretty big margin to reach a different conclusion. The rumor about the engineering library is pretty funny. There are cracks in the hallway around there but I had thought it was just normal settling not sinking due to books!
lets put 3 million peaple in there and get them to jump while caring a army back at full load and see if the ground beneef in still holds.
heck that could distroy the earth. as they say you got to be in to win;>
Taipei 101 causes earthquake ?
….maybe the same scaremongers who postulate that co2 causes global warming; I am very skeptical of them all…..These people don’t have a deep knowledge of science.