What did all those earthquakes near Bluffdale mean?
Mar 25, 2019 11:41AM
By Jennifer Gardiner
Graph shows large amounts of earthquakes hit the Bluffdale area in February (Photo Courtesy U of U Seismology)
By Jennifer Gardiner | [email protected]
After a wave of earthquakes hit the southwest end of the Salt Lake Valley in February, many started to worry if that meant the “big one” was right around the corner. Seismologists weighed in on the concerns and were quick to jump in and try to help ease residents’ fears.
According to The University of Utah Seismograph Stations, 160 earthquakes occurred in the Bluffdale area from Feb. 13 to March 5. The largest of these quakes was a 3.7 magnitude that occurred just after 5 a.m. on Feb. 15.
Jim Pechmann, a seismologist with the University of Utah, with the help of Paul Roberson, said in a report he wrote about the Bluffdale earthquakes, that the largest foreshock was a 3.2 that occurred just shortly before the 3.7.
“One-hundred forty-six of the earthquakes were aftershocks, with the largest being a 3.1 on Saturday, Feb. 23,” said the report. “It is possible the Bluffdale earthquakes are occurring on the nearby Wasatch fault, but it is also possible they are occurring on a minor, unnamed fault.”
The report further stated the 4.0 earthquake that occurred in central Utah on Feb. 20 is not related to the Bluffdale earthquakes, as it is more than 120 miles away, which is too far to trigger a larger earthquake.
No injuries or damages were reported in any of the quakes. Perchmann said in Utah, an earthquake usually needs to be larger than 6.0–6.5 magnitude for a surface break to occur.
“The reason the quakes were felt on the surface by so many was because there are a lot of people living on top of where the earthquakes occurred,” said Pechmann. “A second reason is that the deep soils in the Salt Lake Valley tend to amplify ground motions from earthquakes, especially small ones.”
Perchmann goes on to explain the smaller quakes also do not mean they are releasing pressure to lessen the chances of a larger quake in the near future; smaller quakes only increase the chances of a larger one, not lessen it.
Be Ready Utah says being prepared for an earthquake is very important, that an earthquake larger than any others we have ever experienced in the valley is likely to happen in the future. Utah is a seismically active region, and the majority of Utah’s population is concentrated in the highest area of hazard.
In a press release issued by the Utah Seismic Safety Commission, officials said the Duck, Cover and Hold On procedure is based on the premise that the built environment in the United States is superior to that in many developing countries.
”Because of seismic provisions in building codes, stringent building inspections and superior building materials, the structural collapse of buildings in the United States occurs infrequently,” said the release. “Further, earthquakes have been shown to cause significant non-structural and content damage, for example, caused by falling ceiling and light fixtures and toppled bookcases and cabinets. Falling objects pose a real risk of injury or death.”
The Utah Division of Emergency Services, California Office of Emergency Services, Structural Engineers Association of California and American Red Cross all agree that taking cover under sturdy furniture, such as a desk or table, will greatly reduce the possibility of injury or death.
The main things seismologist want people to know in case of an earthquake is to make sure they have a 72-hour kit with food, water and clothing, along with a home evacuation plan. Residents should also make sure heavier items are not located in a place that could cause severe injury if they fell.
It is also good to discuss a meeting place for your family, as communication grids are likely to go down, making reaching your loved ones difficult. For more information about the Duck, Cover and Hold tips for preparing children and the elderly, as well as other resourceful tips, you can go to www.utah.gov/beready/earthquakePreparedness.