2020 Magna Earthquake Sequence FAQ

Updated March 10, 2021 with additional information on the Magna Sequence here.

Magna earthquakes March 18, 2020 - Feb 2021

How many earthquakes have we had in the area?
The University of Utah Seismograph Stations (UUSS) has located 2,590 earthquakes that occurred in the Magna, Utah, area from March 18 through February 28, 2021(Figure 1). The largest of these earthquakes was the magnitude (M) 5.7 mainshock that occurred at 7:09 am MDT on Wednesday, March 18, 2020. The remaining 2,589 earthquakes are aftershocks. The largest aftershocks were two M 4.6 events that occurred at 8:02 am and 1:12 pm on Wednesday, March 18, 2020. A M 4.2 aftershocks occurred on April 14 and 17th which were widely felt along the Wastach Front. There have been 36 aftershocks of M 3 and larger. We continue to locate new earthquakes as they occur.

Magna earthquakes March 18, 2020 - Feb 2021 magnitude vs Time plot

What is a Foreshock, Mainshock, or Aftershock?

Mainshocks, foreshocks, and aftershocks are all earthquakes. The mainshock is the largest magnitude earthquake in an earthquake sequence. It may be the first event in the sequence or occur later. The earthquakes in the sequence that occur before the mainshock are called foreshocks and the ones that occur after are called aftershocks. Sometimes an earthquake that is initially called the mainshock is reclassified as a foreshock because a larger earthquake follows it. An earthquake sequence is a group of events that occur close together in time in the same area.

What is the difference between UUSS and USGS?

The University of Utah Seismograph Stations (UUSS) and the U.S. Geological Survey (USGS) are partner agencies. All seismic data from the Utah region are collected and initially processed by UUSS. The resulting earthquake locations, magnitudes, and ShakeMaps are submitted to the USGS, which serves the information on a USGS website. USGS personnel often provide additional information on their website related to how the earthquake ruptured, how widely the earthquake was felt, the potential economic and life impacts, and the chances of aftershocks and landslides. As members of the Advanced National Seismic System (ANSS), UUSS and USGS work together to provide the most accurate and complete information about earthquakes in the Utah region.

We had a 5.7 earthquake, what are the percentages of having a larger earthquake soon?

Most likely, the 5.7 earthquake will end up being the biggest earthquake in this sequence and so it will be called the mainshock. There is a small chance, roughly one-in-twenty (5%), that a larger earthquake will occur in the next 5-6 days after the mainshock. In that case, the 5.7 earthquake would be redesignated as a foreshock, and the new, larger earthquake will be called the mainshock.  A “larger” earthquake means any earthquake bigger than the one that just occurred, even if it is only 0.1 magnitude units bigger. The probability of an earthquake being a foreshock to an earthquake that is one or two magnitude units larger is much smaller than one-in-twenty.

How long did the mainshock last?

How long you felt the shaking would depends on where you were.  For the 
Magna Earthquake, if you were downtown, the strongest shaking lasted around 4-6 sec.  However, the shaking was strong enough to be felt for about 20 sec.

Will this delay or trigger “the big one?”

No, small earthquakes do not relieve enough stress in the earth to reduce the likelihood of a large earthquake. We are still at risk of a magnitude 7-7.5 earthquake (the “Big One”) occurring somewhere along the Wasatch fault. The risk is similar to what it was before the Magna sequence. 

How will I be notified of the next earthquake?

Anyone can sign up for Earthquake Notification Service (ENS) and receive emails or text messages about earthquakes as the locations are published. You may set up your own geographic area and magnitude threshold. All UUSS earthquake locations are sent out via the ENS system. Sign up here.

Will the ground open up or Fracture from the 5.7 earthquake?

It is unlikely for the fault rupture from the 5.7 earthquake to reach all the way to the surface and create what we call a scarp. It is possible that shaking from the 5.7 created liquefaction features at the surface near the epicenter. 

Why can’t Utah get a M9.0 Earthquake?

The bigger an earthquake is, the more space on a fault it takes up. The faults in Utah simply are not big enough to accommodate an M9 earthquake.

How does the earthquake depth affect the shaking  and how do you measure the depth?

The shallower the depth of an earthquake, the stronger the shaking will be near the epicenter; however, the strength of shaking will fall off more rapidly away from the epicenter. It is the same idea as aiming a flashlight at a wall and walking toward the wall. The closer you get to the wall the more intense the light becomes, but it takes up a smaller area. Earthquake depth is measured from the arrival times of seismic waves, similar to how the epicenter is determined.

Are earthquakes more common now? 

No. There is no evidence for change in the overall rate that earthquakes occur.

More information from Earthquakes.utah.gov

What can I do to be prepared?
An excellent source of information on earthquake preparedness is the publication “Putting Down Roots in Earthquake Country”.

M 3.5 north of Paragonah, Utah

University of Utah Seismograph Stations
Released: October 30, 2018 03:30 AM MDT

The University of Utah Seismograph Stations reports that a minor earthquake of magnitude 3.5 occurred at 02:15 AM on October 30, 2018 (MDT).  The epicenter of the shock was located beneath the Black Mountains in southwestern Utah, 12 miles north of the town of Paragonah, Utah, and 13 mi SE of the town of Minersville, UT.  This earthquake was reported felt in the city of Milford, Utah.  A total of 19 earthquakes of magnitude 3 or greater have occurred within 16 miles of the epicenter of this event since 1962.  The largest of these events was a magnitude 4.6 in 1991, located in the same area as today’s magnitude 3.5 earthquake.

Anyone who felt the earthquake is encouraged to fill out a survey form on the US Geological Survey website:
https://earthquake.usgs.gov/data/dyfi/ .

Small Salt Lake City Earthquakes Felt and Heard

The University of Utah Seismograph Stations reports that four minor earthquakes of magnitude (M) 0.7 to 1.0 have occurred in northeastern Salt Lake City during the last eight days.  The first two earthquakes occurred on Sunday, September 2, at 02:13 am (M 0.7) and 10:33 am (M 1.0) MDT.  They were followed by an M 1.0 shock on Thursday, September 6, at 8:43 pm MDT and an M 0.8 shock at 3:48 pm MDT on Saturday, September 8.  These four earthquakes occurred near the southeastern part of the University of Utah campus at shallow depths of less than 3.5 miles.

Residents of northeastern Salt Lake City have reported feeling and/or hearing these earthquakes, in some cases describing the noise as a loud boom.  Earthquakes, especially very shallow ones, can generate noises that sound like booms or thunder to those nearby.  The sound is generated by seismic waves vibrating the ground surface up and down like a loudspeaker.

Small magnitude seismic activity like the recent activity in northestern Salt Lake City is a common occurrence in the Wasatch Front region.   The location of this recent activity appears to be too far east for it to be occurring on the Wasatch fault.

Anyone who felt or heard any of these earthquakes is encouraged to fill out a survey form which is available on the US Geological Survey website at https://earthquake.usgs.gov/data/dyfi/ .

Magnitude 3.6 near Panguitch, UT


University of Utah Seismograph Stations

Released: February 28, 2018 08:15 AM MST

The University of Utah Seismograph Stations reports that a minor earthquake of magnitude 3.6 occurred at 07:11 AM on February 28, 2018 (MST).  The epicenter of the shock was located in southwestern Utah near Hatch Mountain, 12 miles SSW of Panguitch, UT. This event was reported felt mostly in Panguitch and surrounding areas. A total of 16 earthquakes of magnitude 3 or greater have occurred within 16 miles of the epicenter of this event since 1962. The largest of these events was a magnitude 3.9 on December 21, 1991, 15 miles WSW of Tropic, UT.  A magnitude 4.6 earthquake occurred on April 20, 1991, 13 miles SE of Minersville, UT.

Anyone who felt the earthquake is encouraged to fill out a survey form either on the Seismograph Stations website: www.quake.utah.edu or the US Geological Survey website: earthquake.usgs.gov.

Earthquake Summary:

Date (UTC):   February 28, 2018         Time (UTC):   14:11

Date (local): February 28, 2018         Time (local): 07:11 AM MST

Latitude:     37 40.21′ N

Longitude:    112 31.84′ W

Preferred magnitude: 3.60 Ml

1902 – Pine Valley, UT (series) – M 6 ±

Intermountain Seismic Belt Historical Earthquake Project

November 17, 1902 – Pine Valley, UT  (series) – 6 ±

In the early afternoon of November 17, 1902 residents of Pine Valley, UT were startled by a magnitude 6 ± earthquake. The shaking caused individuals to flee their homes, some being hit by swaying doors and jambs as they ran. Most of the chimneys in town were reportedly damaged. Clocks stopped. Some individuals reported seeing clouds of dust in nearby canyons as rocks weighing many tons came crashing down. Poultry and domestic animals were frightened. Some individuals reported that upon putting an ear to the ground, they could hear a low roar like a stove burning. Though residents were on edge day and night, no one was reported to have evacuated the area.

To the south, in St. George and Santa Clara, there were reports of considerable damage to many buildings. The shaking was strong enough in some buildings to flip hanging pictures completely over. Terrified children and adults ran from homes and other buildings, some experiencing the sensation of seasickness. Many residents were afraid to reenter their homes. Clouds of dust were seen in many directions from falling rocks as far as 25 miles away. It was reported that in some places, hot and cold springs were increased in their flows and waters became muddy.

The earthquake was reported felt in other cities and towns in the surrounding area including Bloomington, Pinto, Cedar City and Toquerville. Individuals in these areas reported damage such as toppled chimneys, falling ceiling plaster, cracked walls, items toppling from shelves, frightened people rushing from buildings and huge boulders rolling down causing clouds of dust. The communities of Lund, Notom, Parowan, Marysvale and Tropic reported feeling the earthquake but suffering no damage.

Felt reports from Salt Lake City mentioned stopped clocks and jarred nerves but no damage. One establishment reported a substance that appeared to be volcanic ash on its windowsills, causing some to question whether the earthquake had activated extinct volcanoes in the southern part of the state. Some individuals speculated that ash from such a volcano could have been carried northward by strong winds. Closer to the epicenter, a few individuals reported seeing smoke above the Pine Valley Mountains and some reported seeing a flash of fire lasting a few seconds, though others reported detecting no evidence of volcanic activity in the area.

On December 4, it was reported that not a day had passed since the initial shock without one or two earthquakes being felt in Pine Valley. A report from St. George on the same day noted that residents there were rejoicing in the belief that the earthquakes had finally ceased – at that point it had been four days since a shock had been felt.

For additional information about this earthquake:

Earthquake Summary 3D Newspaper Articles 3D Personal Accounts 3D Additional Resources 3D

For more information about this project:

ISB Hist EQ Proj

1934 – Hansel Valley, UT (series) – M 6.6

Intermountain Seismic Belt Historical Earthquake Project

March 12, 1934 – Hansel Valley, UT  (series) – M 6.6

Believed to be the most severe earthquake in Utah’s recorded history, the 1934 Hansel Valley earthquake was reportedly felt as far west as Elko, Nevada and as far east as Rawlins, Wyoming. Felt reports were also issued from as far north as Boise, Idaho and as far south as Richfield, Utah.

The main shock occurred approximately 30 miles north of the Great Salt Lake at 8:05 a.m. local time. Five significant aftershocks were recorded over a nearly eight-week period from March 12 to May 6, 1934.

Some of the most severe damage was reported in Logan, Utah and surrounding communities. At least two public buildings in the area had to be abandoned. A three-story brick building on the campus of the Utah State Agricultural College was, reportedly, split from top to bottom. In Preston, Idaho, the shaking dislodged a 150-pound capstone from the top of the local high school building, separating the west wall from the rest of the building.

Other reports of damage included falling chimneys, broken windows, cracked walls and falling plaster. Swinging light fixtures were observed during the earthquake. Furniture rocked back and forth or rolled across floors. Dishes and goods fell from shelves and clocks stopped. Near the epicenter, in Snowville, Utah, the water main was broken and out of service for 10 hours. In some locations schools were evacuated and closed, particularly following the first aftershock.

Near the epicenter of the earthquake the appearance of several fissures or cracks in the ground surface were observed. Witnesses reported hearing loud roars as the fissures ruptured. A geologist who later examined the area reported one of the fissures to be about eight miles in length. He found a maximum fissure width of 14 inches, with a maximum drop of the ground on one side measuring 19 inches. Other reports noted a downward displacement of the ground on the east of the larger, predominantly north-south trending fissures.

Phenomena described as sand or mud cones were observed near the epicenter. There were also sightings of new springs and streams changing course. Artesian wells that had been long dry began flowing with water. Other wells, active prior to the earthquake, ceased to flow for several hours.

In many locations, shaking from the earthquake sent people running out of doors. There were also reports of people fainting from fright. In areas of intense shaking, people were unable to stand during the earthquake.

Two deaths were attributed to the earthquake. Ida Atkinson died instantly from a heart attack upon hearing that the shaking she felt was due to an earthquake. Salt Lake City waterworks employee Charles Bithel was injured when a six-foot trench in which he was working at the time of the earthquake caved in. Bithel died from his injuries the following day in a local hospital.

For additional information about this earthquake:

Earthquake Summary 3D Newspaper Articles 3D Photos 3D Blank Thumbnail
Personal Accounts 3D Additional Resources 3D Blank Thumbnail Blank Thumbnail

For more information about this project:

ISB Hist EQ Proj

1959 – Kanab, UT – M 5.7

Intermountain Seismic Belt Historical Earthquake Project

July 21, 1959 – Kanab, UT – M 5.7

This earthquake was felt over an area of 21,000 square kilometers, primarily in southern Utah and northern Arizona, according to newspaper accounts. Dishes and canned goods were knocked to the floor, cars were jostled on roads, and minor rockslides occurred. Felt reports were received from as far south as Flagstaff, Arizona–approximately 195 miles from the epicenter.

Near the epicenter, in the Kanab-Fredonia area, there were also reports of windows and dishes breaking, as well as canned goods tumbling from market shelves. In Kanab, the police chief reported bricks falling from at least one chimney. And plaster in the county courthouse was shaken from the walls. A truck driver traveling through the area at the time of the earthquake related that he “thought his steering had gone haywire.”

The earthquake, which occurred at 10:39 am local time, sent frightened Kanab residents scurrying from their homes–but no injuries or significant damage was reported.


For additional information about this earthquake:

Earthquake Summary 3D Newspaper Articles 3D Additional Resources 3D Blank Thumbnail

For more information about this project:

ISB Hist EQ Proj


1915 – Provo, UT – M 5.0

Intermountain Seismic Belt Historical Earthquake Project

July 15, 1915 – Provo, UT – M 5.0


According to newspaper accounts this earthquake was felt throughout the Utah, Salt Lake, and Bear River Valleys, and also in Provo Canyon, Tooele, Parley’s Canyon, and Park City, Utah.  The felt area measured 13,000 square kilometers.

In parts of Utah Valley buildings swayed, chimneys toppled, building walls were cracked, and individuals were knocked from chairs and couches. Wallpaper was split over doors and plaster was cracked and shaken loose. Dishes and pans rattled. In Provo Canyon shaking from the earthquake caused rockslides which blocked at least one road. At Utah Lake an upheaval of water, like a small tidal wave, was sighted.

In the Salt Lake Valley clocks stopped, windows and dishes rattled, and furniture was knocked over. Cans and packages were shaken from grocery store shelves.

Shaking appeared to be more pronounced in the upper floors of taller buildings both in Provo and Salt Lake City. In some locations both in the Utah and Salt Lake Valleys, the shaking caused individuals to rush out of buildings. This was the case throughout Provo where people hurried into the streets wondering what had happened. It was reported that more than an hour passed before the city resumed normal activities.

There were no reports of injuries or significant damage from the earthquake.


For additional information about this earthquake:

Earthquake Summary 3D Newspaper Articles 3D Additional Resources 3D Blank Thumbnail

For more information about this project:

ISB Hist EQ Proj