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Satellite data confirms San Francisco tower sinking

Data from a European Space Agency (ESA) satellite has confirmed that a 58-storey tower in San Francisco is sinking.

The Millennium Tower — completed in 2008 — has been referred to as the “leaning tower of San Francisco.” That’s because soon after completion, residents began to notice that the building was tilted.

The building is tilted five centimetres at the base with a 15-centimetre lean at the top, according to recent measurements. And with the building being an earthquake zone, that’s clearly raised some concerns. 

ESA’s Copernicus Sentinel-1 satellite confirmed, with data collected between Feb. 22, 2015 and Sept. 20, 2016, that the building was sinking four to five centimetres a year.

The new data supports claims that the building isn’t on terra firma. The ESA says the sinking and leaning could be a result of the building not resting firmly on bedrock.

The satellite was also used to take several measurements of the land shifting in and around San Francisco. It showed an uplift of the land in the nearby city of Pleasanton, which could be due to the replenishment of groundwater following a four-year drought.

The city is located near the Hayward fault line, which hasn’t produced a large earthquake in more than 140 years. The last big one was in 1868.

Bay area land displacement

This satellite image shows the land displacement in the San Francisco Bay area. Hotspots can been seen, including along the Hayward fault line at centre right. (Copernicus Sentinel data (2015–16) / ESA SEOM INSARAP study / PPO.labs / Norut / NGU)

According to the U.S. Geological Survey, the past five major earthquakes along this fault have occurred 140 years apart. This could be of particular concern to people living in the building.

Residents of the Millennium Tower filed a lawsuit against the developer earlier this month.