Earthquake swarm continues to shake Southeast Idaho

This map from United States Geological Survey’s website shows the locations of 73 earthquakes that have struck near Soda Springs from Oct. 5 to 11. Forty smaller earthquakes have followed a magnitude 4.1 event that struck on Tuesday evening.

This map from United States Geological Survey’s website shows the locations of 73 earthquakes that have struck near Soda Springs from Oct. 5 to 11. Forty smaller earthquakes have followed a magnitude 4.1 event that struck on Tuesday evening.

By Kendra Evensen, kevensen@journalnet.com 

SODA SPRINGS — Earthquake activity near Soda Springs has picked up again following a 4.1 magnitude quake on Tuesday evening.

Jim Pechmann, a seismologist with the University of Utah Seismograph Stations, said the earthquake occurred approximately 12 miles southeast of Soda Springs around 7:30 p.m.

More than 70 people in Soda Springs, Preston, Pocatello, Montpelier, Afton, Wyoming, and other locations reported feeling the quake.

Of course, there were likely many more who felt something, but didn’t bother reporting it because earthquakes have become a bit of a norm in recent weeks, Pechmann noted.

The earthquakes are all being considered aftershocks from the Sept. 2 Sulphur Peak Earthquake near Soda Springs that had a magnitude of 5.3. Officials with the U.S. Geological Survey reported that there had been more than 1,900 aftershocks as of mid-September, and even more have followed.

USGS officials say the sequence has been a particularly active one and has produced more aftershocks on average than other earthquakes of a similar magnitude.

Pechmann said the activity has slowed down in recent weeks, but has not stopped.

It’s been approximately a month since the area has experienced a magnitude 4 earthquake, Pechmann said, but he added that it’s not surprising to have another one occur, or to see an uptick in activity following the incident.

From Oct. 3 to Oct. 11, USGS’s website said that there were 73 total earthquakes recorded near Soda Springs.

As of 8 p.m. on Wednesday, 40 more smaller earthquakes had followed the magnitude 4.1 event on Tuesday, according to the USGS website. There have been no reports of structural damage or injuries from the quakes on Tuesday and Wednesday.

“Basically, aftershocks can go on for months before dying away completely — sometimes years,” Pechmann said.

Still, he noted that as long as that activity continues, there will be a higher-than-normal chance of a larger earthquake occurring. Luckily, that’s a slim chance.

USGS officials are forecasting three possible scenarios for this month. They say the most likely (90 to 95 percent) is that the sequence will continue to decay.

“Earthquakes above M3 may be felt by those in the area, and occasional spikes in activity may be accompanied by additional M4 or larger earthquakes, but with none larger than the M5.3 mainshock,” according to the forecast updated on Sept. 27.

USGS officials say there is also a 5 to 10 percent chance that a second earthquake of magnitude 5.3 or greater may occur, but that would be unusual.

Finally, they say there is a less than 1 percent chance that a much larger earthquake — up to magnitude 7 — could occur.

“It is important to understand that this is a highly unlikely scenario, but we cannot ignore the possibility of this occurring,” according to the forecast.

Pechmann says it’s always a good idea to be prepared, just in case. He encourages people to keep enough food and water on hand to get through 72 hours, and make sure their families know what to do in the event of an earthquake.

“Don’t run outside,” he said, adding that people should instead crawl underneath a heavy desk or table or stand underneath an interior doorway. “If you’re outside, move away from buildings (and trees) and things that could fall on you.”

Pechmann also encourages people to safeguard their homes. He says it’s a good idea to bring houses up to code as time and resources allow. In addition, he said people should also be careful where they put their belongings. For instance, shelves bearing heavy items shouldn’t be placed over beds.

Even though it’s unlikely that a large earthquake will occur, Pechmann doesn’t think Southeast Idaho residents should ignore the chance, especially since they live in earthquake country.

“People should pay attention to this hazard and do what they can to prepare themselves,” he said.