In the aftermath of the initial seismic event, United States Geological Survey scientist David Wald said that “an earthquake this size has the potential to be damaging anywhere in the world, but many structures in this region are particularly vulnerable”. The 7.8 and 7.5 magnitude earthquake sequence that struck Turkey and Syria on 6 February caused severe damage to infrastructure and the failure of thousands of buildings. “The old expression: ‘when you dug yourself into a hole you should stop digging’ is just particularly applicable in this case.The scale of destruction caused by powerful earthquakes such as the ones that recently struck Turkey and Syria could be reduced through strict adherence to seismic building codes, better risk analysis and comprehensive site investigations, experts say.Īs the death toll from the earthquakes continues to rise, passing 45,000 last week, the scientific and engineering communities are looking for answers, including a UK mission organised by the Earthquake Engineering Field Investigation Team that aims to uncover the causes of the extensive damage and loss of life. He says city building officials should not stand by if the sinking problem continues to get worse. But Hamburger maintains the sinking would have occurred had there been no fix work on the building.Ĭity building officials said in a statement that the data to date falls within “acceptable ranges” and the tower is sinking about the same rate it was during work early last year, before piles were installed.īut Pyke notes monitoring data shows settlement during resumed pile installation and digging running about double the rate logged during the early part of the project. The engineer who designed the fix, Ron Hamburger, has told city officials to expect some additional sinking before the work is completed this fall. “This is like having the man who is leaning forward and you excavate under the toes of his shoes,” he said. Pyke said the new digging comes at a critical time, with the tower already pressing on the soil along Fremont Street from the stresses caused by installation of the piles. “This is uncharted and unpredictable territory,” said another veteran local geotechnical engineer, Bob Pyke, who had separately sounded the alarm about the risks of the fix before work began last year. “So, what you're going to have is a condition gets worse and worse and worse,” Karp said in an interview with NBC Bay Area. Karp and structural engineer Joshua Kardon recently warned city building officials in a letter that more review is needed to account for the “very serious” risks of further sinking and tilting posed by the excavation phase. He said then that the fix would inevitably cause the loss of supportive ground as piles were installed on two sides of the building. Karp first warned city building officials about the risks of the foundation retrofit back in 2019, before work started. “So, as they take all that away, they’re losing lateral support,” said veteran geotechnical engineer Larry Karp. That earth, they say, has acted as a buttress alongside of the existing concrete slab foundation as the building continues to lean. The building rebounded slightly at the northwest corner the following week, but experts worry the settlement at the corner will likely accelerate as more supportive earth is removed at the base. Monitoring data shows the building settled 1/10th of an inch in the week that ended April 4. But data shows the sinking resumed when crews started digging along the northwest edge of the foundation at Mission and Fremont Street to make room for a foundation extension. After crews installed 18 piles in mid-March, the settlement stopped at that corner. The structure is currently leaning 27 inches at the northwest corner. Sign up for NBC Bay Area’s Housing Deconstructed newsletter. Get a weekly recap of the latest San Francisco Bay Area housing news.
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