Geography of the Hazard

Credit: From Adapted from USGS Liquefaction Map

Earthquakes are usually associated with shaking buildings but they can also cause landslides, tsunamis, fires, isolated flooding and collapsed roadways. Fortunately, Stansbury Park is unlikely to suffer a tsunami or landslide because we are hundreds of miles from the nearest ocean and relatively far from the nearest mountain ranges. But, our unique geography still puts us at risk for one specific earthquake hazard—soil liquefaction.

At 30 miles from the Wasatch Fault Zone (WFZ), Stansbury is well inside the expected damage radius of a major quake. In fact, the Missouri University of Science and Technology’s analysis of earthquake damage case studies(6) shows that large structures can be heavily damaged by quakes as far as 200 miles away when soil liquefaction occurs.

Unfortunately, all of Stansbury sits squarely in a high-risk area for soil liquefaction.

What is Soil Liquefaction?
According to the USGS, liquefaction is “the process by which strong shaking during an earthquake causes the ground to temporarily lose its strength and behave like a viscous liquid.”
Further, the USGS also says most of Utah’s population lives on valley land with susceptible soils and shallow groundwater(7). Even among Utah’s overall higher risk, Stansbury Park has the highest anticipated risk because our community sits on land that was once lake bottom. Our high water table and loose soil put us at prime risk.

Credit: Utah Division of Natural Resources

How Does Liquefaction Work?
As P waves travel out from the center of an earthquake, they intermittently compress water between soil grains. This forces the grains apart, making the mixture of soil and water flow like a liquid(7). If soil contains a lot of water, it can be forced to the surface of cause structures to sink into the ground.

Simply put, a high likelihood of soil liquefaction means a higher likelihood that roadways and buildings could become seriously damaged during a quake.