National

Osaka quake highlights dangers posed by concrete-block walls

by Mizuho Aoki and Chisato Tanaka

Staff Writers

The death on Monday of a 9-year-old girl in Osaka Prefecture highlights the potential dangers of violating building codes and of concrete-block walls, which can turn lethal when major earthquakes strike.

Following the incident in the city of Takatsuki, in which a 40-meter-long wall surrounding a school’s swimming pool collapsed and crushed the girl, the Takatsuki Municipal Government apologized and admitted that the wall was in violation of building codes.

City officials said the total height of the structure was 3.5 meters — a 1.6-meter wall on top of a 1.9-meter concrete foundation — exceeding the legal cap of 2.2 meters. It also lacked legally required support blocks, they said.

“I am deeply sorry for the collapse at the school facility, causing the fatal accident. We take on responsibility as it is the city’s property,” Takatsuki Mayor Takeshi Hamada said at a news conference Monday.

The city inspected the wall in January last year, but officials said they were not aware of the dangers posed by concrete-block structures. In the wake of the incident, education minister Yoshimasa Hayashi said Tuesday that he will ask all elementary and junior high school operators nationwide to conduct safety inspections of concrete-block walls near schools.

The city’s failure to detect the vulnerability of the wall during its inspections, however, is not unusual, experts said, noting that similar dangerous structures prone to collapse can be found across the nation. “Many are not aware that their walls could pose serious harm to people if a quake hits. Many leave them as they are without taking any measures,” said Kazuya Koga, a professor at Fukuoka University who is well-versed in disaster prevention.

Koga, who has been studying concrete-block walls across the archipelago, said 70 percent to 90 percent of concrete walls in each municipality do not meet legal standards. Miyagi Prefecture is the only exception due to its strict inspection rules for concrete-block structures.

“I’ve been conducting inspections since the Great Hanshin-Awaji Earthquake in 1995. And I’ve never seen a concrete-block wall that meets the legal standards collapse (after a quake),” Koga said.

“So if the walls were made in accordance with the law, there would be no issue.”

The danger of such walls drew wide public attention in 1978, when 18 people were crushed to death by collapsed blocks following a major earthquake off Miyagi.

Following that tragedy municipalities called on residents to reinforce their concrete walls, with some providing subsidies for property owners. But the efforts were not effective, Koga said.

Miyagi Prefecture went further, hiring experts to check concrete-block walls around schools and sending written warnings to owners of illegally built walls — urging them add reinforcements, Koga said.

“Other municipalities should follow in the footsteps of Miyagi” or similar tragedies could happen again, Koga said.

Masayoshi Saichi, a professor of construction engineering at Tohoku Institute of Technology, echoed this view, noting the high number of concrete-block walls that could collapse easily if a strong quake occurs.

“Aged and illegal concrete-block walls need to be removed and replaced with new ones,” he said.

The education ministry has been retrofitting public elementary and junior high school buildings to make them able to withstand earthquakes measuring 6 on the Japanese seismic intensity scale of 7. As of April 1, 2017, the ministry had completed reinforcement of buildings at 98.9 percent of the schools.

The measure, however, does not cover concrete-block walls in the vicinity of schools.

Information from Kyodo added