SALT LAKE CITY – University of Utah researchers say an unusual sequence of earthquakes that occurred in central Utah in 2018 and 2019 is a reminder that ancient Utah volcanoes in the area are active. Fortunately, they say there is no indication of an impending eruption.
The research, which was first published in Geophysical Research Letters last month, focused on a pair of peculiar earthquake sequences in the Black Rock Desert near Fillmore. One of the central Utah earthquakes occurred on September 12, 2018 and the other on April 14, 2019. The earthquakes registered a magnitude of 4.0 and 4.1, respectively, and produced multiple aftershocks.
The location of both earthquakes was the Black Rock Desert volcanic field 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 flows 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 that was being used less than 20 miles out of the desert to monitor a geothermal well for a different project.
A team of researchers from the University of Utah, USGS, and the University of Iowa went to work 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 earthquake was 1 ½ miles below the surface, which is quite shallow for earthquakes. For example, the 5.7 magnitude earthquake that struck the Wasatch front last year occurred about 6 miles below the earth’s surface; The central Utah earthquakes of 2018 and 2019 were unrelated to the Magna earthquake, the largest in Utah since 1992.
Also, the earthquakes did not produce “shear waves” which are common in Utah earthquakes. The frequency of the seismic energy was also much lower than that of typical Utah earthquakes, said Maria Mesimeri, a postdoctoral research associate at the University of Utah Seismograph Stations and lead author of the study, in a news release Tuesday. .
“Because these earthquakes were so shallow, we were able to measure surface deformation (due to earthquakes) using satellites, which is very unusual for such small earthquakes,” he said.
The data led the researchers to believe that the earthquakes were not caused by colliding faults like most Utah earthquakes; rather, they said their research indicated that these earthquakes were the result of ongoing activity in the volcanic field below the desert.
Mesimeri said both earthquakes were likely caused by magma or hot water that came close to the surface and caused 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,” he said. “The earthquakes could be the result of compression of the fluid through the rock or the result of deformation by the movement of the fluid that stressed the surface faults.”
The good news, he added, is that there is no reason to believe that recent earthquakes are warning signs of an impending eruption. It simply means that it is a location that researchers may want to pay more attention to.