2020 Magna Earthquake Sequence FAQ

The earthquake map, count, and aftershock plot will be updated on Wednesdays around noon.

Epicenter map for 2020 Magna Earthquake Sequence March 18 - June 24

How many earthquakes have we had in the area?
The University of Utah Seismograph Stations (UUSS) has located 2,320 earthquakes that occurred in the Magna, Utah, area from March 18 through June 24, 11 am MDT (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. 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. A M 4.2 aftershocks occurred on April 14 and 17th which were widely felt along the Wastach Front. There have been 40 aftershocks of M 3 and larger. We continue to locate new earthquakes as they occur.

Magnitude vs time plot of Magna Earthquake Sequence, March 18 - June 24

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”.

M4.2 Aftershock, near Magna UT

PRESS RELEASE

University of Utah Seismograph Stations

Released: April 14, 2020 10:15 PM MDT

The University of Utah Seismograph Stations reports that a light earthquake of magnitude 4.2 occurred at 08:56 PM on April 14, 2020 (MDT). The epicenter of the shock was located in the northwestern part of the Salt Lake Valley, 3.3 mi NE of Magna, UT. This earthquake was an aftershock of the magnitude 5.7 earthquake that occurred in the same area on March 18, and was the largest aftershock to occur since the day of the magnitude 5.7 mainshock. Today’s aftershock was widely felt in the Wasatch Front region of Utah, especially in the Salt Lake Valley. To date, the University of Utah Seismograph Stations has located 1,247 aftershocks from the March 18 earthquake, including four others of magnitude 4.0 or larger (all on March 18) and 39 of magnitude 3.0 and larger. The aftershock activity is expected to continue for at least several more weeks, but with the rate continuing to decrease with time.

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

Earthquake Summary:

Date (UTC): April 15, 2020 Time (UTC): 02:56

Date (local): April 14, 2020 Time (local): 08:56 PM MDT

Latitude: 40 43.92′ N

Longitude: 112 3.54′ W

Preferred magnitude: 4.2 Ml

Magnitude 5.7 near Magna, UT

PRESS RELEASE

University of Utah Seismograph Stations

Released: March 18, 2020 8:20 AM MDT

The University of Utah Seismograph Stations reports that a moderate
earthquake of magnitude 5.7 occurred at 07:09 AM on March 18, 2020
(MDT). The epicenter of the shock was located in the northwestern
Salt Lake Valley, 3.1 mi N of Magna, UT. This earthquake was widely
felt throughout the Wasatch Front area of north-central Utah. It
has been followed by numerous aftershocks, including 20 of magnitude
3.0 or larger during the first hour after the M 5.7 and two of
magnitude 4.0 or larger. The largest aftershock so far was a M 4.6
event that occurred at 7:14 am.

Today’s earthquake was the largest earthquake to occur in Utah since
a magnitude 5.9 earthquake in 1992 in southwestern Utah near St. George.
Today’s earthquake occurred in a seismically active part of the Salt
Lake Valley, where six magnitude 3.0 or larger earthquakes have
occurred since 1962. The largest of these events was a magnitude 5.2
on September 05, 1962, 0.8 mi NE of Magna, UT.

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

Earthquake Summary:

Date (UTC): March 18, 2020 Time (UTC): 13:09

Date (local): March 18, 2020 Time (local): 07:09 AM MDT

Latitude: 40 45.11′ N

Longitude: 112 4.65′ W

Depth: 10.7 km

Preferred magnitude: 5.7 USGS Mw

M 3.9 near Tremonton, UT

PRESS RELEASE
University of Utah Seismograph Stations
Released: September 24, 2019 11:00 AM MDT

The University of Utah Seismograph Stations reports that a minor earthquake of magnitude 3.9 occurred at 10:15 AM on September 24, 2019(MDT).  The epicenter of the shock was located north of the Great Salt Lake, 14 miles northwest of Tremonton, UT. 

This earthquake was reported felt throughout northern Utah including in the city of Tremonton and the surrounding communities.  A total of 45 earthquakes of magnitude 3.0 or greater have occurred within 16 miles of the epicenter of this event since 1962.  The largest of these events was a magnitude 4.5 on July 05, 1989, 11 miles west-southwest of Tremonton, UT.

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

Earthquake Summary:

Date (UTC):   September 24, 2019         Time (UTC):   16:15
Date (local): September 24, 2019         Time (local): 10:15 AM MDT
Latitude:     41 48.94′ N
Longitude:    112 23.38′ W
Preferred magnitude: 3.90 Ml

2019 Bluffdale Earthquake Sequence FAQ

Seismicity near Bluffdale, Utah Feb 13- April 20

How many earthquakes have we had in the Bluffdale area?
The University of Utah Seismograph Stations (UUSS) has located 191 earthquakes that occurred in the Bluffdale, Utah, area from February 13 through April 20 (Figure 1).  The largest of these earthquakes was the magnitude (M) 3.7 mainshock that occurred at 5:09 am MST on Friday, February 15.  Of the remaining 190 earthquakes, 13 occurred before the M 3.7 and, in retrospect, are considered to be foreshocks.  The largest foreshock, and the only one larger than M 2.0, was an M 3.2 event that occurred seven minutes before the mainshock.   177 of the earthquakes are aftershocks.  The largest aftershock was an M 3.1 event that occurred on Saturday, February 23, at 2:31 am MST.  There have been eleven aftershocks of M 2.0 and larger, including the M 3.1. Only two aftershocks occurred from April 1 through 20.

Was the M 4.0 earthquake that occurred on Wednesday, February 20, near the town of Kanosh in Central Utah related to the recent Bluffdale earthquakes?
No, the February 20 M 4.0 earthquake in central Utah is not related to the Bluffdale earthquakes.  The distance between these areas of recent earthquake activity is more than 120 miles.  The M 3.7 Bluffdale mainshock was too small to trigger other earthquakes at such a large distance.

Are these earthquakes occurring on the Wasatch Fault?
Within the uncertainties in the data, it is possible that the Bluffdale earthquakes are occurring on the nearby Wasatch fault (Figure 3). However, it is also possible that they are occurring on a minor, unnamed fault. It is generally difficult to know for sure which fault an earthquake is on, due to uncertainties in the locations of both faults and earthquakes below the ground surface.  The main exceptions are when an earthquake is large enough for the fault displacement that caused the earthquake to break the ground surface and create a fault scarp.  In Utah, an earthquake usually needs to be larger than M 6.0-6.5 for a surface break to occur.

Do these small earthquakes make a big one less likely?
No, small earthquakes do not relieve enough stress buildup in the earth to reduce the likelihood of a large earthquake. In fact, every earthquake that occurs has a small, roughly one-in twenty, chance of being a foreshock to a larger earthquake within five days.  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.

Are the recent Blufdale earthquakes unusual?
No, not in the context of statewide earthquake activity.  Small earthquakes occur every day in Utah, although most of them are too small or too far from population centers to be felt.  On the average, the Utah region has one M ≥ 4.0 earthquake per year and one M ≥ 3.0 earthquake per month, not counting foreshocks and aftershocks.  The 2019 Bluffdale earthquakes are within an east-west trending band of seismicity across the southern end of the Salt Lake Valley that has had earthquakes off and on since at least 1971, including events of M 4.1 in 1992 and M 3.2 in 2016 (Figure 3).  The recent earthquakes near Bluffdale serve as a reminder that Utah is earthquake country and a large, damaging earthquake could occur at any time. Therefore, everyone living in Utah should strive to be prepared for large earthquakes.

Historical Seismicity for the Bluffdale, UT area

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 4.1 near Kanosh, UT

University of Utah Seismograph Stations
Released: April 13, 2019 11:55 PM MDT

The University of Utah Seismograph Stations reports that a light earthquake of magnitude 4.1 occurred at 9:59 PM on April 13, 2019 (MDT).  The epicenter of the shock was located near the Twin Peaks in the southern Sevier Desert, 11 miles east-northeast of the town of Black Rock, UT, and 18 mi west of the town of Kanosh, UT.  Two aftershocks occurred within the first hour after the M 4.1 earthquake, a magnitude 2.7 at 10:09 pm and a magnitude 1.7 at 10:32 pm.   Earlier this year on February 20, a magnitude 4.0 earthquake occurred 15 miles east of today’s earthquake and 5.5 miles south-southwest of Kanosh.  A total of 18 earthquakes of magnitude 3.0 to 4.0 have occurred within 16 miles of the epicenter of today’s event since 1962.

Anyone who felt the earthquake is encouraged to fill out a survey form on the US Geological Survey “Did You Feet it?” website.

M 2.4 felt near Saratoga Springs, UT

PRESS RELEASE

University of Utah Seismograph Stations
Released: April 10, 2019 09:45 PM MDT

The University of Utah Seismograph Stations reports that an earthquake of magnitude 2.4 occurred at 08:06 PM on April 10, 2019 (MDT). The epicenter of the shock was located beneath the city of Saratoga Springs, Utah, along the northwestern shore of Utah Lake. This earthquake was reported felt in the northern Utah Valley cities of Saratoga Springs, Lehi, and Eagle Mountain. A total of 8 earthquakes of magnitude 3.0 or greater have occurred within 16 miles of the epicenter of this event since 1962. Earthquakes the size of today’s event or larger occur on the average of once per week somewhere in the Utah region.

Anyone who felt the earthquake is encouraged to fill out a survey form on the US Geological Survey “Did You Feet it?” website.

M 4.5 near Bedrock, Co widely felt in Moab area.

Press Release:

Released: March 4, 2019 11:45 AM MST

The University of Utah Seismograph Stations

The University of Utah Seismograph Stations reports that a light earthquake of magnitude 4.5 occurred at 10:22 AM on March 04, 2019 (MST). The epicenter of the shock was located in Slick Rock Canyon in southwestern Colorado, 2.6 miles south-southwest of the town of Bedrock, Colorado, and 7 miles south-southeast of the town of Paradox, Colorado.
This earthquake was widely felt in southwestern Colorado and southeastern Utah, including the cities of Grand Junction, Colorado, and Moab, Utah. This earthquake was followed by an M 2.0 aftershock at 10:41 am MST. A total of 8 earthquakes of magnitude 3.0 or greater have occurred within 16 miles of the epicenter of today’s earthquake since 1962. The largest of these previous events was a magnitude 4.4 on May 27, 2000, located 2.2 miles northeast of today’s event.

Anyone who felt the earthquake is encouraged to fill out a survey form on the US Geological Survey “Did You Feet it?” website.

M 4.0 Near Kanosh, UT

PRESS RELEASE

University of Utah Seismograph Stations

Released: February 20, 2019 01:45 AM MST

The University of Utah Seismograph Stations reports that a light earthquake of magnitude 4.0 occurred at 12:05 AM on February 20, 2019(MST). The epicenter of the shock was located in central Utah in the southwestern part of the Pavant Range, 5.3 mi south-southwest of the town of Kanosh, UT, and 18 miles southwest of the city of Fillmore. This earthquake was reported felt in the cities of Fillmore, Monroe, and Richfield, Utah. Three small aftershocks occurred within the first 45 minutes after the mainshock, all of magnitude less than 2.0.

A magnitude 3.3 earthquake occurred in the same area last Saturday
at 3:05 pm MST. A total of 28 earthquakes of magnitude 3.0 or greater have occurred within 16 miles of the epicenter of today’s event since 1962. The largest of these earthquakes was a magnitude 4.0 on February 23, 2001, located 8.2 mi southwest of Kanosh. In 1967, a magnitude 5.2 earthquake occurred 23 miles to the southeast of today’s event.

Anyone who felt the earthquake is encouraged to fill out a survey form on the US Geological Survey “Did You Feet it?” website.