SALT LAKE CITY, (ABC4) – Cities are literally sinking worldwide, and new research says that the weight of urbanization may affect the earth’s crust where they build.
Around the world, cities like San Francisco, Jakarta, and Mexico City are experiencing the effect. It’s called subsidence.
The reason scientists are becoming more concerned with the sinking in those areas is as the cities sink, climate change is causing the sea to rise. In San Francisco, it has been reported widely across media outlets the buildings are sinking.
The 58 story Millennium Tower is called the “leaning tower of San Francisco”
A study published on the AGU website says that people are choosing more and more to live in cities across the world. By 2050, 70% of the planet’s population will live in large urban areas. The intense building is causing cities to sink. The study focused on San Francisco, and the model says the area is dropping at rates ranging from 5- 80 mm per year. At the high end, that is 3.1 inches.
In Utah, most construction is located along a section of the Wasatch Front called the Urban Corridor. From Brigham City to Spanish Fork is 108 miles of the most densely populated area of Utah.
Most of the people also live close to the Wasatch Fault.
Can building in Utah cause the area to sink? Could the weight of the buildings create enough stress to cause earthquakes?
The answer is no. It’s not likely to happen in Utah because of the different makeup in our area’s geological structure.
According to Geologist Mark Milligan with the Utah Geological Survey, the state is geologically a unique place. But even with 108 miles of building along the Urban Corridor, the scale of that building doesn’t compare with what nature has done to Utah already.
Milligan says, “The scale of our buildings is minute compared to the earth’s crust here.”
Utah is part of the basin and range area of North America, and even though earthquakes in this area are caused by the valley floors moving down as the mountains move up, the way construction is done along the Wasatch Front is not as heavy as the Oquirrh Mountains or the Wasatch Range.
Katherine Whidden, a Research Seismologist at the University of Utah, says, “As far as I know construction does not cause earthquakes. Human-induced seismicity occurs in mining, deep well injection, and reservoir/dam building.”
Milligan backs her statement up and explains that most of the time humans cause surface-level seismic activity. The events are not as massive as an earthquake, “but seismographs detect the activity.”
When construction is done in Utah, there is planning to account for the settling because of our geology. Milligan explains, “There are local issues, like areas near Utah Lake, The Great Salt Lake, or Ogden where there are problems with the settling and landslides. But on the whole, it’s not as big a problem as in other places.”
Where Utah gets hurt, is the old buildings– they are not designed or reinforced for a ground-shaking event.
Small issues of unstable ground, geologically speaking, are not anything like what is happening in San Francisco or the other cities.
But how can the Wasatch Front hold the weight? According to Milligan, “Lake Bonneville use to be on top of the entire thing. The water weight alone is more than all of the building that’s been done along the Wasatch Front.”
Utah and the rugged landscape may ultimately be stronger than we think.
