Residents at a high-rise commercial residential building in Seongsu-dong in Seoul’s Seongdong district lodged complaints about vibrations they felt within the structure. Experts speculate that the vibrations would most likely have been detected due to resonance. Resonance is a phenomenon in which violations that have occurred outside of a building coincide with the frequency of the building’s own vibrations to magnify the scale of vibrations.
According to the Seongdong Fire Station on Sunday, a compliant about vertical vibrations was lodged to the station at around 4:30 pm on Thursday from Acro Seoul Forest, a commercial residential building complex in Seongsu-dong, on Sunday. The complaint was mostly lodged by residents on 4th, 17th and 27th floors.
Fire and disaster officials who were mobilized to the scene checked earthquake detection devices at the disaster prevention center in the basement but failed to detect any violations. The building’s builder, DL E&C, also conducted an emergency safety inspection on Friday, but concluded it had nothing to do with the structural problem or safety of the building.
Experts believe that the tremor was mostly likely caused by resonance inside the building. “It has been confirmed that the tremor was not affected by external factors including earthquake, winds, exterior finish work and blasting with explosives,” Park Hong-geun, professor of architectural engineering at Seoul National University who participated in an emergency safety inspection. “Group dancing or warm up exercise by performers at an entertainer management company could have been the cause.”
The building comes with 33 stories and seven underground levels, and an entertainer management company is occupying floors sixth through 19th, with four of these floors used as dance training halls. “When the building vibrated, window glass was cracked and floor surface turned bumpy,” a 24-year-old employee at the company said.
Experts believe that the latest tremor in the building was similar to ‘resonance’ that rocked Techno Mart Building in Gwangjin-gu, Seoul in 2011. Experts concluded at the time the tremor occurred when 23 people at a fitness center on 12th floor stamped their feet 2.7 times per second in tandem to perform taebo dance.
“We have installed gauges at some of the floors and are constantly monitoring to detect the exact cause of the vibration,” DL E&C said.