SALT LAKE CITY – Researchers from the University of Utah say an unusual series of earthquakes that occurred in central Utah in 2018 and 2019 is a reminder of the area’s ancient Utah volcanoes. Fortunately, they say there is no evidence of an impending eruption.
The research, first published last month in Geophysical Research Letters, centered around a few peculiar earthquake sequences in the Black Rock Desert near Fillmore. One of the earthquakes in central Utah occurred on September 12, 2018, and the other occurred on April 14, 2019. The earthquakes registered 4.0 and 4.1 in magnitude, respectively, causing several aftershocks.
The site of both earthquakes was the Black Rock Desert volcanic field located in central Utah between I-15 and the Utah-Nevada state line. The volcanic area last erupted about 720 years ago, resulting in basalt cinder cones and flowing through Ice Springs, according to the US Geological Survey.
In addition to the earthquakes detected by the Utah Regional Seismic Network, they were captured by temporary seismic equipment used less than 20 miles from the desert to monitor a geothermal source for another project.
A team of researchers from the University of Utah, USGS and the University of Iowa set to work on analyzing the data. The temporary equipment helped detect 35 aftershocks after the 2019 earthquake, which was almost double what the normal system detected.
They found that the quake was a mile below the surface, which is quite shallow for earthquakes. For example, the 5.7 magnitude earthquake that rattled the Wasatch Front last year occurred about 6 miles below the Earth’s surface; the 2018 and 2019 central Utah earthquakes were unrelated to the Magna earthquake, Utah’s largest earthquake since 1992.
In addition, the earthquakes did not produce the “shear waves” common in Utah earthquakes. The frequency of the seismic energy was also much lower than typical Utah earthquakes, Maria Mesimeri, a postdoctoral research associate for University of Utah Seismograph Stations and the study’s lead author, said in a news release Tuesday.
“Because these earthquakes were so shallow, we were able to measure the surface deformation (caused by the earthquakes) using satellites, which is very unusual for such small earthquakes,” she said.
The data led researchers to believe the earthquakes were not caused by colliding faults like most Utah earthquakes; They previously said their research indicated that these earthquakes were the result of continuous activity in the volcanic field beneath the desert.
Mesimeri said it is likely that both earthquakes were caused by magma or heated water moving closer to the surface that triggered the earthquakes.
“Our findings suggest that the system is still active and that the earthquakes were likely the result of fluid-related movements in the general area,” she said. “The earthquakes could be the result of the fluid squeezing through rock or the result of deformation from fluid movements highlighting the surface defects.”
The good news, she added, is that there is no reason to believe that the recent earthquakes are warning signs of an impending eruption. It just means it is a location that researchers may want to pay more attention to.