M5.7 Utah Earthquake

On March 18, 2020, a 5.7 earthquake struck Magna, UT just outside of Salt Lake City. The earthquake occurred along Utah’s Wasatch Front, a major area of concern for FEMA preparedness and the subject of FEMA 2021 National Level Exercise. Thankfully, there were no casualties or major injuries as a result of the tremors, but our Hazus team was quick to act in order to conduct an economic loss evaluation in order to determine where the priority may lie for mitigation and relief.

Graph indicating low likelihood of casuality
PAGER graphic indicating low likelihood of human casualty

This particular earthquake is one of the largest ever recorded in the area since 1934, when a M6.6 earthquake struck during March of that year. Earthquakes of M7 caliber are expected to happen roughly every 1,300 years according to geological studies of the Wasatch fault. The March 18, 2020 event showed at least 26 seismic documentations exceeding M5 within 250km of Magna.

While there were no reported casualties or serious injuries, our Hazus reports indicate a significant amount of economic damage, in the range of $629,000,000. Of that number, $62,000,000 accounts for building damage, including 18,603 residential damaged structures. Hazus modeling results were used in the governor of Utah’s request to the White House for a Presidential Disaster Declaration to address damages from the March 18 earthquake.

Preliminary loss estimates were all conducted remotely in the wake of the COVID-19 pandemic.

Not insignificant either is the number of structures damaged that were unreinforced masonry buildings, or URMS. As stated by Geologists and Engineers for Earthquake Safety at Utah Earthquake Safety, “A URM is a building in which the primary supporting walls are brick, blocks, stone, adobe, or concrete (masonry) that does not have adequate steel or wood structural support to properly withstand shaking associated with a severe earthquake.” These structures are a greater risk of damage in the event of an earthquake or other seismic activity.

Our findings show that these unreinforced buildings received more damage due to the nature of their structure. Such findings support those that are emphasized by local Utah initiatives such as Fix the Bricks, a program to help fund fixes and safeguards for those who live in URMs in the Salt Lake region. 

Our Hazus team participated in an Unreinforced Masonry Risk Reduction meeting organized by FEMA during the conference to help make sure Hazus is serving agency-wide efforts to characterize risk and mitigation opportunities in major earthquake-prone areas, in particular the Wasatch Front in Utah. We presented original research demonstrating the importance of using updated infrastructure data in Hazus risk assessments.

For more information, view the HAZUS Results Dashboard for Utah Earthquake 5.7, or the USGS PAGER.

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