Five years ago today, northern Utah was shaken by the M5.7 Magna earthquake. Since then, the University of Utah Seismograph Stations has recorded >2800 aftershocks, 90% of which occurred in the first year following the mainshock. Even though it has been five years, the aftershock sequence is ongoing. In the past 12 months, UUSS has recorded 49 earthquakes within 15 km (9 mi) of the mainshock, with magnitudes ranging from -0.2 to 2.5. This number of earthquakes is significantly above the background seismicity rate of <10 earthquakes a year in the same area. Aftershocks decrease in both number and magnitude as time passes, and even though the sequence is ongoing we don’t necessarily anticipate any more of the larger aftershocks that were felt throughout the Salt Lake Valley in the days and weeks following the 2020 mainshock.
For more information on Magna and Utah earthquakes:
Magna: https://quake.utah.edu/monitoring-research/2020-magna-earthquake-sequence
Utah earthquakes: https://earthquakes.utah.gov/
Earthquake preparedness: https://beready.utah.gov/
Where were you when the 2020 Magna earthquake hit?