Kusunoki Koichi, a professor at the Earthquake Research Institute of the University of Tokyo, has spent time surveying buildings in Turkey, a country prone to regular seismic activity.
He says this month's magnitude 7.8 tremor caused many low-rise and middle-rise buildings to collapse instantly when their pillars gave way. "This is a very dangerous phenomenon called a 'pancake' collapse, where the entire building collapses downwards on itself."
No time to escape
Violent shaking first causes the pillars of a multistory building to explode. That leads to each floor of the building falling and folding.
Professor Kusunoki says the reason why casualties are so high is that when a 'pancake' collapse occurs, people inside have no time to escape.
While the earthquake resistance building code in Turkey is the same as in Japan, many old buildings do not meet those standards. Professor Kusunoki says it will be crucial to look at the ages of the buildings that collapsed and the precise causes of the failures.
He also notes that multiple housing complexes toppled over on the same side.
Professor Kusunoki says it's possible that major damage has occurred even in buildings that meet Japanese seismic standards.
"Although Japan's seismic diagnosis and reinforcement are progressing, there are still buildings that were designed according to old standards. It is very important to keep working on seismic reinforcement."
Comparing against the Japanese scale
Earthquake engineer Shiomitsu Masashi, an assistant professor at Yamagata University, has been analyzing seismometer data obtained from about 30 observation points in Turkey. The tremor occurred shortly after 4:00 a.m. local time on February 6.
Shiomitsu notes that the quake generated severe shaking equivalent to a seismic intensity of 7 on Japan's seismic intensity scale of zero to 7 in Hassa, Hatay region, about 60 kilometers southwest of the epicenter.
In recent decades, three quakes in Japan have generated the same seismic intensity: the Great Hanshin-Awaji Earthquake in 1995, the Great East Japan Earthquake in 2011, and the Kumamoto Earthquake in 2016. All three caused catastrophic damage.
Shiomitsu also reports that during the Turkey earthquake, shaking equivalent to a Japanese scale upper and lower 6 extended to a range of about 160 kilometers from the epicenter.
He warns that tremors of that size could cause serious damage to relatively large structures, such as middle-rise buildings in Japan. "It's believed that very powerful tremors with an intensity of upper 6 to 7 on the Japanese seismic intensity scale, which can cause severe damage to buildings in Japan, were the reason for the extensive damage, but we need to confirm this."