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.

M 3.7 near Blufdale, UT

PRESS RELEASE

University of Utah Seismograph Stations Released: February 15, 2019 06:45 AM MST

The University of Utah Seismograph Stations reports that a minor earthquake of magnitude 3.7 occurred at 5:09 AM on February 15, 2019 (MST).  The epicenter of the shock was located at the southern end of the Salt Lake Valley, 1.8 miles south of the town of Bluffdale, UT.

This earthquake was preceded by a magnitude 3.2 foreshock at 5:02 am and was followed by six aftershocks, all smaller than magnitude 2.

This morning’s earthquake was reported felt by more than 7,000 residents of the Salt Lake Valley and Utah Valley.  The foreshock was also reported felt.  Since 1962, five earthquakes of magnitude 3.0 or greater have occurred within 16 miles of the epicenter of today’s event.  The largest of these events was a magnitude 4.1 on March 16, 1992, located six miles west-southwest of Bluffdale, UT.

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

Magnitude 3.8 near Enterprise, UT

Press Release

Released: January 16, 2019 03:30 PM MST

The University of Utah Seismograph Stations reports that a minor earthquake of magnitude 3.8 occurred at 03:00 PM on January 16, 2019 (MST).  The epicenter of the shock was located in southwestern Utah, 1.4 miles south of Upper Enterprise Reservoir and 10 miles SW of the town of Enterprise, UT.  A magnitude 2.8 foreshock occurred two minutes before the magnitude 3.8 earthquake.  Ten other earthquakes have occurred in this same area during the past week, ranging in magnitude from 0.8 to 2.9.  Earthquake activity in this area is not unusual.  A total of 11 earthquakes of magnitude 3.0 or greater have occurred since 1962 within 16 miles of today’s earthquakes.  The largest of these events was a magnitude 4.3 on January 15, 2016, located 12 miles WSW of the town of Enterprise.

Today’s M 3.8 earthquake was reported felt in the town of Central, UT, 14 miles NE of the epicenter, and in the town of Ivins. UT. Anyone who felt the earthquake is encouraged to fill out a survey form on the US Geological Survey “Did You Feet it?” website.

M 2.8 Near Bountiful, UT Felt Along Wasatch Front

Press Release

Released: October 23, 2018 11:45 PM MDT

The University of Utah Seismograph Stations reports that an earthquake of magnitude 2.8 occurred at 10:30 PM on October 23, 2018 (MDT). The epicenter of the shock was located beneath the Wasatch Range, 11 miles east of the city of Bountiful, UT, and 12 miles south of the city of Morgan, UT. This earthquake was reported felt by residents of Wasatch Front communities extending from Salt Lake City on the south to Kayesville on the north, with most of the reports coming from the cities of Bountiful, Centerville, and Farmington.

A total of 5 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 3.3 on June 11, 2014, 10 miles east of Centerville, UT.

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

PRESS RELEASE

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