2020 Magna Earthquake Sequence FAQ

Map of epicenters for the Magna Earthquake Sequence March 18-27

How many earthquakes have we had in the area?
The University of Utah Seismograph Stations (UUSS) has located 658 earthquakes that occurred in the Magna, Utah, area from March 18 through March 30, 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 657 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. There have been 33 aftershocks of M 3 and larger. Many (hundreds and perhaps thousands) smaller earthquakes have yet to be located and will be posted in the coming days. We also continue to locate new earthquakes as they occur.

Magnitude vs time plot of Magna Earthquake Sequence, March 18-30

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.

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. 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.

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

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

Seismograph Technician Opening at UUSS

The University of Utah Seismograph Stations is seeking a specialist who will work under the supervision of other professional staff to operate, repair, and maintain 230 stations forming part of the University of Utah’s regional seismic network. Stations consist of seismic sensors, digital data acquisition systems, and associated telemetry equipment and are sited both in the urban built environment and in remote field locations throughout Utah and in parts of neighboring states. The Seismograph Technician will assist with the installation of new seismograph stations and maintain a detailed record of station visits and a written repair history for specified equipment items.

More information can be found here.

Installed SM instrument in building
Installed Strong-Motion Building Intallation

Magnitude 4 earthquake near Milford, UT

PRESS RELEASE

University of Utah Seismograph Stations

Released: January 16, 2020 08:30 PM MST

The University of Utah Seismograph Stations reports that a light earthquake of magnitude 4.0 occurred at 07:31 PM on January 16, 2020 (MST).  The epicenter of the shock was located in southwestern Utah beneath the Mineral Mountains, 10.4 mi SE of the town of Milford, UT and 6 mi NNE of Minersville, UT.  The shock was reported felt by residents of Milford and Cedar City as well as other nearby localities. The earthquake was followed by a magnitude 1.5 aftershock that occurred nine minutes later.

Today’s earthquake occurred in a seismically active area of Utah.   total of 17 earthquakes of magnitude 3.0 or greater have occurred within 16 mi of the epicenter of this event since 1962.

The largest of these events was a magnitude 3.9 on April 10, 1998, 1.4mi NNE of Milford, UT.  In 1991 a magnitude 4.6 earthquake occurred 13 miles SE of Minersville.

Anyone who felt the earthquake is encouraged to fill out a survey form on the US Geological Survey website: https://earthquake.usgs.gov/earthquakes/eventpage/uu60356907/tellus.

Earthquake Summary:

Date (UTC):   January 17, 2020         Time (UTC): 02:31

Date (local): January 16, 2020         Time (local): 07:31 PM MST

Latitude:     38 17.50′ N

Longitude:    112 52.43′ W

Preferred magnitude: 4.00 Ml

UUSS invited to become a formal Member-Institution of the International Seismological Centre (ISC).

The University of Utah Seismograph Stations (UUSS) is excited to announce it was recently invited to become a formal Member-Institution of the International Seismological Centre (ISC).

The ISC is a non-governmental, non-profit international organization which maintains extensive information about earthquakes and other seismic events from around the world. ISC members strive to collect, archive, and process seismic station and network bulletins and prepare and distribute the ISC bulletin – the definitive summary of the world’s seismicity.

Since its inception in the 1960s, the ISC has provided invaluable data used by thousands of seismologists worldwide. The current ISC mission is to maintain the ISC bulletin, the International Seismographic Station Registry, and the IASPEI Reference Event list. ISC also maintains several other important catalogs, contacts, and datasets.

The UUSS is honored to join the ISC. It joins 68 other research and operational organizations in 50 countries that support the ISC. Other ISC Members in the United States include NEIC/USGS, IRIS, and the TexNet of the University of Texas at Austin. The invitation to join comes as a great recognition of the important work of the UUSS on a national, and now international, scale.

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

M 3.5 near southern boundary of Yellowstone National Park

University of Utah Seismograph Stations

Released: August 15, 2019 02:30 PM MDT


The University of Utah Seismograph Stations reports that a minor earthquake of magnitude 3.5 occurred at 01:46 PM on August 15, 2019 (MDT).  The epicenter was located on the southern boundary of Yellowstone National Park,  22.2 miles southeast of West Thumb Geyser Basin and 48.7 miles northeast of Jackson, WY.  Earthquake activity in this location is not unusual.  A total of 9 earthquakes of magnitude 3.0 or greater have occurred since 1962 within 16 miles of todays earthquake.  The largest of these events was a magnitude 4.3 on August 21, 2003 located 22.5 miles south-southeast of West Thumb Geyser Basin and 44.2 miles north-northeast of Jackson, WY.

There have been no felt reports for todays earthquake at the time of this writing.  Anyone who felt the earthquake is encouraged to fill out a survey form either on the University of Utah Seismograph Stations website: www.quake.utah.edu or the U.S. Geological Surveys website: earthquake.usgs.gov.

Earthquake Summary:
Date (UTC): August 15, 2019 Time (UTC): 19:46
Date (local): August 15, 2019 Time (local): 01:46 PM MDT
Latudute: 44 7.66’ N
Longitude: 110 22.73’ W
Preferred magnitude: 3.5 Ml

2017 Annual Report

2017 Annual Report Cover Page

2017 Annual Report

I am happy to report the University of Utah Seismograph Sta- tions (UUSS) had another exciting and productive year in 2017. Thanks to all of you who support and promote our mission of reducing the risk of earthquakes in Utah through research, edu- cation, and public service.

An Mw 5.3 earthquake on Sept. 2, 2017, in southeastern Idaho reminded us that we absolutely do live in earthquake country. Thankfully, this earthquake caused little damage, but its shaking was felt throughout northern Utah, as far south as Provo. UUSS responded to the earthquake by partnering with the U.S. Geo- logical Survey and the Idaho Geological Survey to deploy a tem- porary array of seismographs in the source region. Using these data, we detected and located over 1,000 aftershocks in the two months following the mainshock. This allowed us to map out a previously unknown fault system.

UUSS also recorded enhanced seismicity in Yellowstone Na- tional Park during 2017. Between June 12 and Sept. 30, a swarm of over 2,400 earthquakes was recorded in the Maple Creek re- gion of Yellowstone. The largest event in the swarm was an Mw 4.4 earthquake on June 15 that was widely felt throughout the park. Although earthquake swarms in Yellowstone are common, this was the second longest swarm ever recorded. Yellowstone earthquake swarms are often related to the movement of fluids in the crust and usually do not portend a volcanic eruption; howev- er, it remains important to monitor them closely.

In 2017, UUSS continued working with the University of Utah team vying to host the Frontier Observatory for Research in Geo- thermal Energy (FORGE). This project is sponsored by the U. S. Dept. of Energy and aims to build a facility for developing tech- nologies related to enhanced geothermal energy production. The UUSS FORGE effort is led by Prof. Kris Pankow and is focused on quantifying the seismic hazard near the proposed FORGE site in Milford, Utah. Utah is one of two finalists for this project, and the winner will be announced in 2018.

We look forward to another exciting year in 2018. I encourage you to visit our web page at quake.utah.edu to stay up-to-date on our initiatives and products as well as to find out about the lat- est seismic activity in Utah and Yellowstone. You can also follow UUSS on Twitter with the handle @UUSSquake.

Best wishes, Keith D. Koper

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.