2020 Magna Earthquake

Utah experienced a magnitude (M) 5.7 earthquake on March 18, 2020 at 7:09 a.m.

Interactive Earthquake Intensity Map - United State Geological Survey

On the morning of Wednesday, March 18, 2020, northern Utah experienced a magnitude (M) 5.7 earthquake with an epicenter north of Magna, Utah. The mainshock was widely felt across the Wasatch Front with over 30,000 felt reports received by USGS and UUSS. More than 2,500 aftershocks occurred after the initial M5.7 earthquake. Utah experienced occasional spikes of felt aftershocks of M4.0 or M3.0 for weeks and months afterward.

The count includes:
1 in the magnitude 5.0 – 5.9 range
6 in the magnitude 4.0 – 4.9 range
30 in the magnitude 3.0 – 3.9 range
137 in the magnitude 2.0 – 2.9 range
698 in the magnitude 1.0 – 1.9 range
1,507 in the magnitude 0 – 0.9 range
111 less than magnitude 0 or undetermined

View the USGS Summary

Aftershocks

The University of Utah Seismograph Stations (UUSS) has located 2,590 earthquakes that occurred in the Magna, Utah, area from March 18, 2020, through February 28, 2021. The largest of these earthquakes was the magnitude (M) 5.7 mainshock that occurred at 7:09 a.m. on Wednesday, March 18. The remaining 2,589 earthquakes were aftershocks. The largest aftershocks were two M4.6 events that occurred at 8:02 a.m. and 1:12 p.m. on Wednesday, March 18. Two M4.2 aftershocks occurred on April 14 and 17th which were widely felt along the Wasatch Front.

Timeline of Magna earthquakes March 18 - April 7, 2020 (Utah Geological Survey)

Magna Quake Anniversary Town Hall

In March 2020, a 5.7M earthquake hit Magna, UT. What were the impacts? What did we learn from it? How should we prepare mentally and physically for the next one? Hear from the experts what you can do to help yourself, your family, and your community be ready for the next one.

Wade Mathews, CPM, MEP PIO/Be Ready Utah Section Manager, Division of Emergency Management

Keith D. Koper, Professor in Dept. of Geology & Geophysics, Director of Seismograph Stations, University of Utah

Clint S. Mecham, Director/Battalion Chief Salt Lake County Emergency Management/Unified Fire Authority Division

Emily Kleber, Project Geologist with the Geologic Hazards Program at the Utah Geological Survey in Salt Lake City, Utah.

John Crofts, MBA, CFM Utah Earthquake Program Manager, Utah Division of Emergency Management

Kevin Broderick, LMFT Crisis Counselor, Utah Strong Recovery Project, DHS

Geology of the Magna Earthquake

2020 M5.7 Magna, Utah Earthquake Locations
Updated: February 28, 2021, with 2,451 events

The M5.7 earthquake and subsequent aftershocks occurred in bedrock. Valley deposits of clay, silt, sand, and gravel in the area are between 200 and 1000 feet thick. The earthquake and aftershocks occurred at depths of about 1 to 8 miles. During the earthquake, the bedrock slid past itself along a crack called a fault. Before the earthquake, friction along the fault kept the bedrock from moving. Then, when stresses in the rock finally built up to overcome the frictional resistance on the fault, the bedrock moved and the stress was released, causing the earthquake. With each break (or rupture) of a fault, the rocks around the earthquake adjust and move in the same fashion; this period of adjustment is shown by the grouping of aftershocks. Based on data from the Magna sequence, several research papers now suggest the sequence occurred on the Salt Lake City Segment of the Wasatch fault.

Interactive 3D Model of Magna Earthquake Sequence

Geologic Features

Preliminary Models and Research

Prior to the Magna earthquake, the exact location of the Wasatch fault was unknown, but many scientists thought it dipped at a steep angle deep beneath the Salt Lake Valley. Based on data from the Magna sequence, several research papers now suggest the sequence actually occurred on the Salt Lake City Segment of the Wasatch fault. Evidence also suggests that the fault curves to a gentler angle and is not as deep beneath the surface as previously thought. Multiple research papers conclude that because of the likely gentler dip of the fault, which would put it closer to the surface, ground shaking may be higher than previously estimated for future earthquakes on the Salt Lake City segment of the Wasatch fault. Additional research published to date includes increasing the number of detected earthquakes through machine learning, testing novel methods for magnitude determination, and documenting the challenges of responding to an earthquake during a pandemic.

This conceptual model illustrates one possible scenario for the location of the M5.7 Magna earthquake and its aftershocks relative to the Wasatch fault and associated faults. The M5.7 earthquake and some of its aftershocks might be on the Wasatch fault or on another nearby fault in the network of faults known as the Wasatch fault system. It is difficult to know for certain which fault or faults these earthquakes occurred on because the locations of these faults at depth are poorly known.

View More Research

Damages and Assistance

No major injuries were reported from the mainshock or aftershocks. Damages occurred throughout the valley with the most severe damage in Magna. HAZUS, software used by the state to estimate potential losses, shows that there could be upwards of $62 million in building-related damages, contributing to $629 million in total economic losses related to buildings. This does not include damages to public infrastructure.

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Magna Quake Frequently Asked Questions

For more general earthquake FAQs, visit our homepage FAQs section.

Geology:

▸What are the chances of a larger earthquake or the “Big One” occurring after the M5.7 Magna earthquake in 2020?

In the Magna earthquake sequence, the magnitude (M) 5.7 was the largest earthquake. There was a small chance, roughly one-in-twenty (5%), that a larger earthquake would have occurred in the 5 to 6 days after the initial M5.7 earthquake.

The Magna earthquake has not changed the long-term probabilities of a large magnitude earthquake along the Wasatch Front. A single small earthquake series does not relieve enough stress in the earth to reduce the likelihood of a large earthquake. We are still at risk of a M7.0 to M7.6 earthquake (the “Big One”) occurring somewhere along the Wasatch fault zone. The risk is similar to what it was before the Magna sequence.

In general, the Wasatch Front has the potential to experience an earthquake larger than M7.0, up to a maximum of about M7.6. In 2016, the Working Group on Utah Earthquake Probabilities published a 50-year earthquake forecast for the Wasatch Front region, indicating a 43% probability, or about a 1-in-2 chance, of having one or more earthquakes of M6.75 or greater and a 57% probability, or greater than a 1-in-2 chance, of having one or more earthquakes of M6.0, in that time period. The March 18, 2020, Magna earthquake did not significantly increase or decrease this probability.

▸Where can I see the locations of recent earthquakes?

▸How do you know the difference between an aftershock and other earthquake activity?

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.

▸How long did the 2020 Magna M5.7 earthquake last?

▸Does Utah normally have earthquakes like the 2020 M5.7 Magna earthquake?

▸Is it normal to see aftershock locations scattered?

▸Which fault zone did the 2020 Magna M5.7 earthquake originate from?

After analyzing seismological data, the scientific community mostly agrees that the M5.7 mainshock and majority of aftershocks were related to the Wasatch fault zone on the west side of Salt Lake Valley (Source). The fault line is on the east side of the valley, near the Wasatch mountain front, but dips at an angle below the surface, which is why the earthquake epicenter is on the opposite side of the Salt Lake Valley. Using seismometers that measure seismic energy released by earthquakes, seismologists have used data from the Magna earthquake sequence to modify models of what the Wasatch fault zone fault looks like beneath our feet and, importantly, what the dip of the fault is. Data from the Magna earthquake indicate that ground shaking in the Salt Lake City region in future Wasatch fault earthquakes may be higher than previously estimated.

As of September 2020, the Magna earthquake sequence has generated over 2,300 aftershocks. This number of aftershocks since the mainshock in March 2020 follows a normal pattern observed from earthquakes worldwide. Some of the aftershocks clustered in a small zone about 3 miles east of the main area of aftershocks, near the Salt Lake International Airport. These aftershocks occurred closer to the surface than the M5.7 mainshock, and seismological data and analysis indicate that these aftershocks in the West Valley fault zone were triggered by the mainshock. Modern seismic data confirm what geologists have inferred from studying the ancient geologic deposits of the West Valley fault zone and Wasatch fault zone.

Watch the 2020 Magna Earthquake Reconnaissance Briefing from the Earthquake Engineering Research Institute (EERI) for more analysis.

Learn more about UGS investigations into the earthquake history of the West Valley fault zone here:

▸Has there been any evidence of surface rupture/displacement from the 2020 Magna M5.7 earthquake?

No evidence of surface fault rupture has been observed. It is unlikely for the fault rupture from a magnitude 5.7 earthquake to propagate all the way to the ground surface and create what we call a scarp. In the Intermountain West, surface rupture generally only occurs with earthquakes larger than about magnitude 6.5.

The magnitude 5.7 earthquake did create liquefaction features, including small cracks and sand boils at the surface near the epicenter.

Learn more about Liquefaction Hazards

▸Is it possible fracking could have caused the 2020 Magna M5.7 earthquake?

▸How does magnitude change farther away from the epicenter?

The magnitude (for example, magnitude 5.7) represents the amount of energy released by the earthquake and is the same everywhere. The intensity of shaking, however, varies from place to place, and is quantified by something called the Modified Mercalli Intensity Scale (for example, Intensity IV). Shaking intensity is generally reduced farther away from the earthquake’s epicenter. This is a function of reducing energy as the earthquake waves travel. There are cases where the shape of the valley or type of sediments can amplify earthquake energy and cause greater shaking.

The estimated intensity of the 2020 Magna M5.7 earthquake in Salt Lake Valley and surrounding areas can be seen on the ShakeMap produced by the U.S. Geological Survey: View Intensity Map
The public also responded to the event with what they felt. View Community Intensity Map

▸Since 1962 the Bingham Canyon mine has deposited a roughly 2.5 billion ton mine tailings pile near Magna. Could this loading induce an earthquake?

▸How many earthquakes did we have in the Salt Lake area from the 2020 Magna M5.7 earthquake?

The University of Utah Seismograph Stations (UUSS) has located 2,590 earthquakes that occurred in the Magna, Utah, area from March 18 through September 18, 11 am. The largest of these earthquakes was the magnitude (M) 5.7 mainshock that occurred at 7:09 am on Wednesday, March 18. The remaining 2,319 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. Two M 4.2 aftershocks occurred on April 14 and 17th which were widely felt along the Wasatch Front.

The count includes 1 in the M5 – 5.9 range; 6 in the M4–4.9 range; 30 in the M3 – 3.9 range; 137 in the M2 – 2.9 range; 698 in the M1 – 1.9 range; 1507 in the M0 – 0.9 range and 83 < M0. There were also 28 earthquakes where no magnitude could be determined.

U of U Seismograph Stations
View the 3D Graphic showing the earthquake focal points beneath the surface.

▸How can I be notified of the next earthquake?

▸Are the aftershocks moving closer to the Wasatch fault zone? The recent aftershocks feel different than before. Is this normal?

▸Was the 2020 Magna M5.7 earthquake in the forecast?

In 2016, the Working Group on Utah Earthquake Probabilities (WGUEP) published a 50-year forecast for moderate to large earthquakes in the Wasatch Front region. They determined there was a 93% chance of having one or more earthquakes of magnitude 5 or larger in that time period. Given that high probability, the March 18, 2020, magnitude 5.7 Magna earthquake was an expected earthquake.

It’s important to understand that the Magna earthquake was not “The Big One” that Utah residents hear about from time to time. The Wasatch Front area has the potential to experience an earthquake larger than magnitude 7, up to a maximum of about magnitude 7.6, which would result in far greater and wide-ranging damage, injuries, and likely deaths. In their 50-year forecast, the WGUEP determined there is a 43% probability, or about a 1-in-2 chance, of having one or more earthquakes of magnitude 6.75 or greater in that time period.

The Magna earthquake should be a reminder that Utahns live in earthquake country, and that there is a reasonable chance that people living in Utah today could experience a large earthquake in their lifetime. As a society, we shouldn’t fear the future, but we should prepare for it.

social:

▸How do I deal with all the fear and anxiety associated with earthquakes?

One way to cope with a major issue, is to learn more about it. The handbook Putting Down Roots in Earthquake Country (Spanish version - Echando Raíces en Tierra de Terremotos) provides information about the threat posed by earthquakes in Utah, particularly along the Wasatch Front, and explains how you can prepare for, survive, and recover from these inevitable events.

Be Ready Utah Disaster Psychology

Buildings built in Utah after about 1975 were built to various building codes with seismic design provisions. As time went on, the building codes and seismic provisions used in Utah were improved (became more stringent), based in part from building performance data resulting from previous earthquakes and damage and paleoseismic investigations performed by the Utah Geological Survey and others. Modern buildings are relatively safe from collapse during earthquakes.

▸Why do I keep feeling phantom earthquakes? Is that normal?

Generally, people are unable to feel earthquakes below about magnitude 2.5 or so. However, certain soil and valley basin effects are known that can cause earthquakes of about magnitude 1.5 or greater to be felt. You might be located in one of these areas and are feeling a small aftershock.

After a stressful situation, our minds and bodies feel like they are replaying feelings for us. This is a very common anxiety response after an earthquake, as well.

▸I keep seeing rumors, where do I find the most reliable information?

Please be very wary of non-official information, such as from various social media feeds. Reliable information on earthquakes is available from the Utah Geological Survey, the University of Utah Seismograph Stations, the Utah Division of Emergency Management, and the U.S. Geological Survey. As with all information, determine if it is from a reliable source and plausible before making decisions and if the information is questionable, verify it first.