The Leaning Tower of San Francisco

The Millennium Tower in San Francisco is confounding engineers because it is sinking at a rapid and terrifying rate. It was originally estimated to be sinking at one inch every year, which is frightening enough, but recent data shows that it is sinking more like 1.6 to 1.8 inches in a year.

The Sentinel-1 satellites have been watching the tower for 17 months, finding that it sunk almost 2.9 inches during that time. Engineers had tunneled under the building to try to understand why it was sinking, but the new data from the satellite is giving the engineers something to think about.


The 58-story building is one of the tallest and heaviest concrete structures within a seismic region. It is built on a landfill and is actually not anchored down, it was expected to settle and shift about 6 inches into the landfill, but unfortunately it has sunk more than 16 inches and is now tilting significantly to the northwest.

According to the Millenium Litigation website, homeowners are experiencing issues with “uneven floors, difficulty opening and closing doors, windows, and cabinets, and that some interior wall cracks have been observed.” The building was only built in 2009, which seems way too early for these sorts of problems.

Millennium Partners, the developer of the building, has insisted that it is “safe for occupancy and could withstand an earthquake.” Which is good in San Francisco, but if the building has tilted and sunk so much in such a short time, what would serious seismic activity do?

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