Techno-Mart is a 39-story shopping mall located in Seoul, South Korea. On July 5, 2011, the building was evacuated due to significant vibrations experienced at upper floors. Originally, the cause of the vibrations was a mystery, as there was no seismic activity. That is, until a most unlikely hypothesis was advanced: Tae Bo.
The aerobic sport combines martial arts and boxing and is typically practiced in groups with vigorous music in the background. During the event that led to nearly approximately 3,000 people being forced to evacuate, according to some reports, a Tae Bo class was practicing on the 12th floor of the building. Concerns over the structural integrity of the building were forwarded to the Architectural Institute of Korea.
A team of experts placed monitors in the building, and set out to recreate the circumstances causing the phenomena. How? Forensic Tae Bo! (Now a lot of us in the forensic industry have maybe put on a few pounds or not spent as much time at the gym as we might like, so perhaps this isn’t such a bad idea after all…)
“We used a laser Doppler vibrometer while performing the same kind of aerobic exercise that was performed at the time of the shaking which occurred on July 5. We noticed that the shaking was felt in the upper floors while the exercise was being performed but no other place showed signs of vibrations,” said Chung.
Mechanical resonance is the most likely explanation for the vibrations, according to the inspectors.
“It just happens to be that the vibration set up by the “taebo” exercises coincided with the resonance frequency unique to the building,” the professor said. When an external vibration hits the resonance frequency of a certain object, the vibration is amplified and causes excess shaking even from slight movement.