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 of the old Utah volcanoes in the area. Fortunately, they say there is no sign of an impending eruption.
The research, which was first published in Geophysical Research Letters last month, focused around a pair of strange earthquake sequences in the Black Rock Desert near Fillmore. One of the earthquakes in central Utah happened on September 12, 2018, and the other happened on April 14, 2019. The earthquakes were recorded with a magnitude of 4.0 and 4.1, respectively, and produced several aftershocks.
The location of both earthquakes was the volcanic field of the Black Rock Desert, 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 ash cones and streams of 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 used less than 20 miles of desert to monitor a geothermal well for another project.
A team of researchers from the University of Utah, USGS and the University of Iowa began working on the data analysis. 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 half a mile below the surface, which is quite superficial for earthquakes. For example, the magnitude 5.7 earthquake that shook the Wasatch Front last year occurred about 6 miles below the earth’s surface; the 2018 and 2019 Utah earthquakes were not related to the 1992 Magna earthquake, the largest in Utah.
In addition, earthquakes did not produce “shear waves,” which are common for Utah earthquakes. The frequency of seismic energy was also much lower than typical Utah earthquakes, Maria Mesimeri, a postdoctoral research associate for the University of Utah’s seismic stations and lead author of the study, said in a news release Tuesday.
“Because these earthquakes were so shallow, we could measure the deformation of the surface (due to the earthquakes) using satellites, which is very unusual for such small earthquakes,” she said.
The data led researchers to believe that the earthquakes were not caused by fault collisions, like most earthquakes in Utah; rather, they said that their research indicated that these earthquakes were the result of continuous activity in the volcanic field below the desert.
Mesimeri said both earthquakes may have been caused by either magma or heated water that came close to the surface and caused the quakes.
“Our findings suggest that the system is still active and that the earthquakes were probably the result of fluid-related movement in the general area,” she said. “Earthquakes could be the result of fluid squeezing through the rock or the result of deformation from the movement of the fluid that highlighted surface defects.”
The good news, she added, is that there is no reason to believe that recent earthquakes are warning signs of an impending eruption. It just means it’s a location that researchers might want to pay more attention to.