The district surrounding Tokyo Disneyland may have to reinforce reclaimed land housing 96,000 people after last week’s magnitude-9 earthquake turned the ground to mud, snapping utility pipes and tipping buildings.
The quake triggered ground liquefaction, which causes soil to act like quicksand, across much of the 1,455 hectares (3,600 acres) of reclaimed land in Urayasu city, said Kazuhisa Nakatani, a local government spokesman. Some of Disneyland’s parking lot was also affected, trapping as many as 30 cars. The main park areas didn’t suffer as they sit on 15-meter (49-foot) deep reinforced foundations.
“There’s no question the earthquake damaged the area more than expected,” said Yasuhiko Hino, the head of urban disaster prevention projects at the Ministry of Land, Infrastructure, Transport and Tourism. Houses in the suburban district were most affected as they lack the concrete pilings that protected high-rise buildings, he said.
Urayasu may consider reinforcing the reclaimed land, which makes up about three-quarters of its surface area, once it has finished dealing with emergency repairs following the March 11 earthquake, Nakatani said. At least one more runway at Tokyo’s Haneda Airport may also be strengthened to bolster defenses following the March 11 quake, the fifth largest ever recorded.
“I was very surprised there was land damage to an area like Urayasu, so far from the seismic center of the quake,” said Yasuo Tanaka, a professor of geotechnical engineering at Kobe University. “They should have been prepared for earthquakes, but given the damage, it clearly wasn’t enough.”
Ground liquefaction caused many buildings to lean over in the 1995 Kobe quake, particularly around the port area, he said. Toughened regulations since then helped prevent failures on solid ground in last week’s temblor, he said.
The reclaimed land in Urayasu was built of mud and sand in the 15 years ended 1980. Reinforcing work could entail inserting pipes to extract water, installing steel piles or pouring in concrete, said Tanaka. Concrete would be the most expensive option, he said.
Any reinforcement work would require “a huge budget,” said Urayasu’s Nakatani. The city, bordering the eastern edge of Tokyo, is about 400 miles from the epicenter of the quake. The temblor and a subsequent tsunami may have killed more than 20,000 people in Japan’s northeastern Tohoku region, based on government figures.
All four of the runways at Haneda, Asia’s second-busiest airport, were built on reclaimed land. None was damaged by the quake. At least one of the two unreinforced strips may be strengthened, said Keitaro Samizo, assistant to the head of the transport ministry’s aviation-planning division.
Tokyo’s Odaiba Island, home to Fuji Media Holdings Inc.’s headquarters, is also built on reclaimed land and experienced liquefaction, according to Minoru Saito, a spokesman for the Tokyo Metropolitan Government’s Disaster Prevention division. No damage to utility pipes or other facilities that would disrupt residents’ lives occurred, he said. While the city has disclosed areas that are prone to liquefaction, it has no plans to conduct any large-scale land fortification, he said.
The last major earthquake to strike Tokyo and its environs directly was in 1923, when more than 140,000 people were killed. The city of about 13 million is adjacent to three major fault lines, including the Nankai Trough, which produces a large quake every 118.8 years on average. The last one, with a magnitude of 8.4, was in 1854.
Repair work on Disneyland’s car parks is almost finished, said Hiroshi Kitamura, a spokesman for operator Oriental Land Co. The park, which opened in 1983, has been closed since the temblor as Tokyo battles power shortages and transport disruption.
A Sapporo Holdings Ltd. beer-processing plant in Funabashi, near Urayasu, damaged in the quake also remains shut, spokesman Tatsuya Komatsu said today.
Shigeyuki Nishinoyama, 54, who lives on the second floor of a six-story block in Urayasu with his wife, said that the quake caused part of his building’s parking lot to collapse. There were no gas supplies until yesterday and the main waterpipe is still broken, leaving the couple without running water, he said.
Nishinoyama said he was warned about the risk of liquefaction when he bought the house and he has no plans to leave the area.
“I like the community and feel even closer to them after this ordeal,” he said.