Unusual earthquakes illuminate Utah volcanoes in the center

Volcanic basalt rocks in the Black Rock Desert, Utah.

If you head south through central Utah on Interstate 15 and look west somewhere around the Fillmore, you’ll see flat hills and fields of black rock. The area is aptly named the Black Rock desert. It may not look like much, but you are looking at some Utah volcanoes.

A pair of series of earthquakes, in September 2018 and April 2019, focused scientists ’attention on the Black Rock Desert. The series, which included the major earthquakes and aftershocks, was very different from the Magna earthquake that shook the 2020 Wasatch Front and other Utah earthquakes. The Black Rock series was captured by the Utah Regional Seismic Network and by the use of a nearby seismic equipment that monitored a georegulatory well. Earthquakes in the Black Rock Desert are extremely rare and the capture of the seismic records from these earthquakes gives us a glimpse of the volcanic system of the Black Rock Desert which, although not showing signs of explosion, still active. A study of earthquake layers is published in Geophysical Research Letters.

“The results showed us that we should pay more attention to the Black Rock area,” said Maria Mesimeri, a postgraduate research associate with the University of Utah Seismograph Stations. “We need to develop seismic and volcanic research in this area, so that we are aware of any small changes that may occur. “

Or your usual earthquakes

The Black Rock desert of Utah. Orange triangles show the location of the University of Utah Seismograph Stations. Black dots indicate the location of Utah earthquakes.

The earthquake series, with major movements of magnitude 4.0 and 4.1 respectively, were constructed by both the Utah Regional Seismic Network and a temporary dense network of seismometers used as part of Utah FORGE, an experimental georegulatory project funded by the U.S. Department of Energy and run by the University of Utah, located about 19 miles south of the Black Rock Desert near Milford, Utah. The temporary network allowed researchers to find more traces than usual. For example, the regional network detected 19 earthquakes as part of the April 2019 series. But the temporary dense network detected an additional 35 earthquakes. Each additional review provided a little more information to seismologists studying the series.

The Black Rock series showed some interesting features that set them apart from the 2020 Magna series and other Utah earthquake series. Although the first Magna earthquake occurred at a depth of about six miles below the surface, a normal depth for Utah earthquakes, the Black Rock earthquake was much thinner – about 1.5 miles below the surface.

“Because these earthquakes were so shallow,” Mesimeri says, “we were able to measure surface deformation. [due to the quakes] using satellites, which is very unusual for such small earthquakes. “

Also, Mesimeri and her colleagues found, the earthquakes produced much lower seismic energy than is typically seen in the Utah earthquake. And none of the major types of seismic waves, shear waves or S-waves, have been found in the Black Rock series.

Volcanoes? In Utah?

Volcanic rocks found in the Black Rock Desert, Utah.

All of these signs indicate that the Black Rock series has a very different origin than the Magna series, which was created by the Wasatch Fracture movement. On the other hand, the Black Rock earthquake may have been generated by continued activity in the Black Rock volcanic area.

What are Volcanoes Doing in Central Utah? The Wasatch Mountains (and Wasatch Fault) make up the eastern edge of an area called the Basin and Range region that extends west to Sierra Nevada. The continent is stretched apart by tectonic plates, which extend out the crust, allowing more heat to rise from the Earth’s interior. In the Black Rock area, that heat caused basalt lava eruptions up to about 9,000 to 12,000 years ago.

So what do these earthquake sequences mean for the Black Rock Desert volcanoes?

“Our findings suggest that the system is still active and that the earthquakes may have been due to fluid-related movement in the general area,” Mesimeri says, referring to magma. which may be present or heated water. “The earthquakes could be the result of the stream pushing through a rock or as a result of deformation from fluid movement that put pressure on the surface cracks.”

Activity in a volcanic area does not mean an eruption, and Mesimeri says there is no evidence of an eruption in the Black Rock Desert. However, she says, this is an area that geoscientists may want to keep a closer eye on.

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Find the full review here.