Earthquakes continue in Southeast Idaho, but exact number is hard to pinpoint

US Geological Survey image The circles show the epicenters of the 260 earthquakes that have hit Southeast Idaho since Sept. 2, according to the U.S. Geological Survey.

US Geological Survey image
The circles show the epicenters of some of the earthquakes that have hit Southeast Idaho since Sept. 2.

By Journal Staff

While it’s clear that an earthquake swarm that has been shaking Southeast Idaho since Sept. 2 hasn’t stopped yet, the exact number of quakes that have occurred is harder to define.

According to the U.S. Geological Survey (USGS), there had been 19 more quakes as of Monday afternoon, bringing the total to 282 since Sept. 2. However, the University of Utah Seismograph Stations reported only 17 new quakes as of Monday afternoon, and a total of 226 since Sept. 2.

Dr. David Pearson, an Idaho State University geologist who studies earthquakes, says the University of Utah has its own seismic network. The USGS uses some of the university’s stations, but the organizations do separate analyses.

The biggest disparity was during the first three days of the swarm — Sept. 2 to 4, when USGS reported that 45 quakes occurred each of those days for a three-day total of 135 quakes compared to the three-day temblor total of 96 from the University of Utah.

USGS reported that there were 23 quakes last Tuesday, compared to the 20 reported by University of Utah, 29 on Wednesday compared to the university’s 25, and a combined 17 Thursday and Friday compared to the university’s 10.

Both USGS and University of Utah reported the same number of quakes on Saturday — 19, while they reported 40 and 39, respectively, on Sunday.

Both organizations recently deployed temporary seismic stations to the area to get better data and help in their studies, which Pearson says is a common practice. He expects their numbers to be closer in the future as a result.

Still, Pearson said the reports can depend on the factors considered, like the magnitude of the quake and the amount of good data available.

In fact, he said it’s likely that there have been several thousand earthquakes in recent days, but most weren’t reported because they were either too small or in a location that made it hard to get data.

Pearson says he was told there were closer to 1,300 quakes on Sunday morning alone.

All of the quakes reported by USGS and University of Utah are occurring in the Caribou County area to the east, southeast and northeast of Soda Springs. The quakes have been felt throughout Southeast Idaho and in Logan, Ogden and Salt Lake City in northern Utah.

Both USGS and University of Utah reported that the most powerful quake in the swarm was a 5.3 magnitude temblor that occurred on Sept. 2.

It’s been years since Southeast Idaho has experienced a 5.0 or greater magnitude quake. Although such temblors can cause damage to buildings, authorities have not reported any damage to structures as a result of the recent quakes.

Authorities have said that Southeast Idaho has never experienced so many quakes in such a short time frame, though the region does experience some seismic activity especially in the Caribou County area.

While some residents have wondered if the quakes could be connected to mining activities in that area, Pearson said he’s pretty confident that they aren’t. The mining activities in southeast Idaho occur at shallow levels and no where near the depths of the quakes, he said.

Pearson said it’s not unusual for aftershocks to continue for days or weeks after an incident. Although there’s a chance that the quakes could lead to another large event, he says the likelihood is low.

USGS officials agree.

“It is fairly unlikely that a large and damaging earthquake will occur, but that likelihood will remain elevated as long as the aftershocks continue,” USGS officials said in a Tetonic Summary about the recent quakes.

Below is advice from the U.S. Department of Homeland Security via https://www.ready.gov/earthquakes on what to do if an earthquake hits your community:

Before An Earthquake

  • Before an earthquake occurs, secure items that could fall or move and cause injuries or damage (e.g., bookshelves, mirrors, light fixtures, televisions, computers, hot water heaters. Move beds away from windows and secure any hanging items over beds, couches, cribs or other places people sit or lie.
  • Practice how to “Drop, Cover, and Hold On!”
    • Plan and practice how to Drop to the ground, Cover your head and neck with your arms, and if a safer place is nearby that you can get to without exposing yourself to flying debris, crawl to it and Hold On to maintain cover.
    • To react quickly you must practice often. You may only have seconds to protect yourself in an earthquake.
  • Store critical supplies (e.g., water, medication) and documents.
  • Plan how you will communicate with family members, including multiple methods by making a family emergency communication plan.
  • Consult a structural engineer to evaluate your home and ask about updates to strengthen areas that would be weak during an earthquake.When choosing your home or business to rent or buy, check if the building is earthquake resistant per local building codes.

During An Earthquake

If you are inside a building:

    • Drop down onto your hands and knees so the earthquake doesn’t knock you down. Drop to the ground (before the earthquake drops you!)
    • Cover your head and neck with your arms to protect yourself from falling debris.
      • If you are in danger from falling objects, and you can move safely, crawl for additional cover under a sturdy desk or table.
      • If no sturdy shelter is nearby, crawl away from windows, next to an interior wall.Stay away from glass, windows, outside doors and walls, and anything that could fall, such as light fixtures or furniture.
    • Hold on to any sturdy covering so you can move with it until the shaking stops.
    • Stay where you are until the shaking stops. Do not run outside. Do not get in a doorway as this does not provide protection from falling or flying objects, and you may not be able to remain standing.
    • If getting safely to the floor to take cover won’t be possible:
    • If getting safely to the floor will be difficult, actions before an earthquake to secure or remove items that can fall or become projectiles should be a priority to create spaces..
    • Identify an away from windows and objects that could fall on you.  The Earthquake Country Alliance advises getting as low as possible to the floor. People who use wheelchairs or other mobility devices should lock their wheels, bend over, and remain seated until the shaking stops. Protect your head and neck with your arms, a pillow, a book, or whatever is available.If you are in bed when you feel the shaking:
    • If you are in bed: Stay there and Cover your head and neck with a pillow. At night, hazards and debris are difficult to see and avoid; attempts to move in the dark result in more injuries than remaining in bed.If you are outside when you feel the shaking:
    • If you are outdoors when the shaking starts, move away from buildings, streetlights, and utility wires. Once in the open, “Drop, Cover, and Hold On.” Stay there until the shaking stops.If you are in a moving vehicle when you feel the shaking:
    • It is difficult to control a vehicle during the shaking. If you are in a moving vehicle, stop as quickly and safely as possible and stay in the vehicle. Avoid stopping near or under buildings, trees, overpasses, and utility wires. Proceed cautiously once the earthquake has stopped. Avoid roads, bridges, or ramps that the earthquake may have damaged.

After an Earthquake

    • When the shaking stops, look around. If the building is damaged and there is a clear path to safety, leave the building and go to an open space away from damaged areas.
    • If you are trapped, do not move about or kick up dust.
    • If you have a cell phone with you, use it to call or text for help.
    • Tap on a pipe or wall or use a whistle, if you have one, so that rescuers can locate you.
    • Once safe, monitor local news reports via battery operated radio, TV, social media, and cell phone text alerts for emergency information and instructions.
    • Check for injuries and provide assistance if you have training. Assist with rescues if you can do so safely.
    • If you are near the coast, learn about tsunamis in your area. If you are in an area that may have tsunamis, when the shaking stops, walk inland and to higher ground immediately. Monitor official reports for more information on the area’s tsunami evacuation plans.
    • Use extreme caution during post-disaster clean-up of buildings and around debris. Do not attempt to remove heavy debris by yourself. Wear protective clothing, including a long-sleeved shirt, long pants, work gloves, and sturdy, thick-soled shoes during clean-up.
    • Be prepared to “Drop, Cover, and Hold on” in the likely event of aftershocks.