On the morning of April 19, 2026, residents in southern Millard County experienced a series of small earthquakes. While earthquakes often spark concern about a larger disaster, seismologists identify these specific events as an earthquake swarm—a common but fascinating geological phenomenon tied to Utah's tectonic history.
What is an Earthquake Swarm?
Unlike a typical earthquake, which starts with one large "mainshock" followed by smaller aftershocks, a swarm is a cluster of many small-to-moderate earthquakes that occur in a short window of time without a single dominant event.
Think of a standard earthquake like a "snap" of a dry twig. A swarm is more like a bag of popcorn—many small pops occurring rapidly as energy is released in increments across a wide area.
The Kanosh Swarm - Facts
- Start Time: Sunday, April 19, 2026, at approximately 5:45 a.m. MDT.
- Total Events: As of April 20, at least 32 earthquakes have been recorded in this swarm.
- Largest Event: A magnitude 3.6 quake recorded at 8:43 a.m.
- Location: Roughly 8 miles south of Kanosh and 18 miles south of Fillmore, directly east of the Black Rock Desert.
Why Did This Earthquake Swarm Occur Here?
The location of this swarm is not accidental. This earthquake swarm occurred along the eastern margin of the Basin and Range Province. This zone of earthquake activity is also called the Intermountain Seismic Belt, and it stretches down the spine of Utah. In this region, the earth's crust is thinning and stretching in an east-west direction, causing the crust to break and shift along faults and producing earthquakes in the process. It also occurred along the eastern side of the Black Rock Desert volcanic field, a region known as being the youngest volcanic area in Utah.
While this swarm is not evidence of an impending volcanic eruption, the plumbing of the ancient volcanic system in the Black Rock Desert is still active. Its possible earthquake swarms in this area are triggered by fluid migration. Deep underground, heated water or gases (like COâ‚‚) move through tiny cracks in the Earth's crust. As these fluids move, they act like a lubricant, causing small, "shattered" faults to slip and slide, causing small earthquakes.
What Does This Earthquake Swarm Mean?
Seismologists from the University of Utah Seismograph Stations (UUSS) emphasize that these swarms are typically self-contained, and typically fizzle out on their own.
While the shaking can be unsettling, it is completely normal, and a sign of the Earth adjusting to pressure in one of North America's most geologically active regions! As always, earthquakes and earthquake swarms like this are a good reminder that Utah is earthquake country, and individuals and businesses should always be prepared for a large earthquake.
For more information on earthquakes in Utah and how to prepare for them, see Putting Down Roots in Earthquake Country at https://roots.geology.utah.gov/.
Additional information is available at https://earthquakes.utah.gov/.
For earthquake preparedness information, see BeReadyUtah at https://beready.utah.gov/.
For real-time seismic monitoring of earthquakes in Utah, see the University of Utah Seismograph Stations at https://quake.utah.edu/.