60-plus aftershocks follow magnitude-6.5 earthquake in Idaho, avalanche closes Idaho 21
There have been 67 aftershocks reported since Tuesday evening’s magnitude-6.5 earthquake that shook Boise and the Treasure Valley.
The U.S. Geological Survey said the earthquake had an epicenter in the mountains northwest of Stanley and 45 miles west of Challis. One of the stronger aftershocks reported had a 4.1 magnitude and happened at around 7:30 a.m. Wednesday, about 40 miles southeast of Cascade.
USGS reports that the aftershocks are a normal result of an earthquake.
“When there are more earthquakes, the chance of a large earthquake is greater, which means that the chance of damage is greater,” according to the USGS website.
The forecast USGS releases following an earthquake states that over the next week, there is a “4% chance of one or more aftershocks that are larger than magnitude 6.5.” USGS reports that it is likely there will be smaller earthquakes over the next week, with a wide range of three to 710 aftershocks that could register at magnitude 3 or higher.
Is the earthquake related to SLC or Yellowstone?
Don Blakeman, a geophysicist for USGS, told the Idaho Statesman on Wednesday that experts do not believe Idaho’s earthquake was connected to the earthquake near Salt Lake City last month.
“There’s no specific way that we can figure out scientifically about why it would happen now,” Blakeman said when asked about the timing.
The general answer, he said, is that the Earth’s crust is broken up into tectonic plates, which are are slowly moving, and when stress builds in those rocks, the energy is released in the form of an earthquake. Earthquakes cannot be predicted.
“Over the next few weeks probably there will be aftershocks,” he said. “... What that means is, as time goes by, there will be fewer and fewer aftershocks.”
After an earthquake as strong as Tuesday’s, Blakeman said he anticipates one or two aftershocks that are about magnitude 5.5.
As of 10 a.m. Wednesday, USGS has reported 37 aftershocks near the epicenter of the Idaho quake, and the largest was a magnitude 4.4.
While the Tuesday earthquake was felt most strongly in Idaho, Blakeman said it was reportedly felt in Washington, Oregon, Montana, parts of Wyoming and a few other areas.
Some Idahoans have been questioning whether the recent earthquakes will have an impact on Yellowstone’s volcanic activity, but Blakeman said he doesn’t anticipate it could trigger an eruption.
“In general I would say no, but we have seen large earthquakes trigger some very small quakes in Yellowstone,” Blakeman said. “It’s possible, but in general we don’t see that. ... I would not expect this to trigger the big eruption at Yellowstone.”
Road closure on stretch of Idaho Highway 21
An avalanche after the earthquake has closed a stretch of Idaho 21, according to the Idaho Transportation Department.
The Idaho Transportation Department reported that the road between Warm Springs Creek Airport Road and the Custer and Boise County line, about 23-35 miles south of the Stanley area, was closed Wednesday.
ITD spokesman Jake Medler said the department closed Idaho 21 around 2 p.m. Tuesday in anticipation of an avalanche because they received heavy snowfall in previous days. When the earthquake happened a few hours later, rocks and snow did fall.
Because ITD and USGS anticipate aftershocks that could cause another avalanche, crews have not cleared the road.
Medler said ITD plans to do a fly-over to survey the damage on the highway. As of Wednesday morning, ITD did not know the extent of the debris on the road or whether the road itself had been damaged.
Rockfall reported on highways, no bridge damage
In a press release Wednesday afternoon, ITD indicated that several mountain highways had rocks tumble onto them as a result of the earthquake.
ITD found rockfall on Idaho 75 near Stanley, on Idaho 21 north and south of Lowman, on Idaho 55 between Horseshoe Bend and Cascade, and on Idaho 52 east of Emmett.
Maintenance crews were quickly sent out after the earthquake to clear the roads. ITD indicated that aftershocks could knock more rocks loose, but crews are patrolling higher-risk areas and clearing roads if necessary.
ITD also announced that as of Wednesday there was no immediate damage to Idaho’s bridges, and highways remain open.
Crews will continue to analyze bridges and buildings closer to the earthquake’s epicenter, the release said.
Idaho hospitals undamaged after quake amid pandemic
Both of the major health systems in Idaho said they are still operating as normal and their buildings were not damaged in the earthquake.
A St. Luke’s Health System spokesperson said over Twitter on Tuesday that the St. Luke’s hospitals did not sustain damage from the earthquake. The news comes amid a global pandemic while Idaho reports over 500 confirmed coronavirus cases.
St. Luke’s spokesperson Anita Kissee said hospitals in Boise, Nampa, Meridian, McCall, Wood River, Mountain Home, Fruitland and the Magic Valley all passed post-earthquake inspections.
Saint Alphonsus Health System spokesperson Mark Snider said Wednesday morning that none of their clinics or hospitals were damaged. Saint Al’s has hospitals in Idaho and Oregon.
“Because no visitors are permitted in our hospitals due to the ongoing COVID-19 pandemic, our staff assisted patients in calling their families, or we called on their behalf, to reassure them that their loved ones were safe and there was no damage to our facilities,” Snider said in an email to the Statesman.
Crosses damaged at Catholic Church
While damage to homes remained relatively minimal in Idaho, one of Boise’s oldest churches saw some damage to its iconic crosses on Tuesday night.
Three of the four historic crosses on top of the Cathedral of St. John’s the Evangelist Catholic Church, at 807 N. 8th St., are cracked, according to Gene Fadness, spokesman for the Roman Catholic Diocese of Boise. The cathedral was built in 1921.
One cross will need to be replaced, but the other damaged ones are believed to be salvageable, Fadness said.
“There was no damage to the inside, including the large stained-glass windows and the rose windows in the loft, for which we are very grateful,” Fadness said in an email. “No one was inside the church. It was locked at the time.”
Checking for gas leaks
Intermountain Gas, which provides natural gas services to Treasure Valley residents, said it received roughly 150 calls from customers between Tuesday and Wednesday.
Intermountain Gas spokesman Mark Hanson said Wednesday that the customer calls came from across the valley, and they ranged from technicians finding a “small leak at the meter where a fitting needed tightening” to no issues at all.
No major incidents have been reported by Intermountain.
Statewide, the Idaho Department of Lands, Division of Minerals, Public Trust, and Oil and Gas said in a news release Wednesday that it is working with operators to conduct initial checks on oil and gas wells in Payette County. No initial problems have been found.
“Initial checks on surface mines across the state also have not indicated any problems,” according to the Department of Lands’ news release. “...The main focus will be on facilities and water handling operations to ensure that earthen dams and holding ponds have not been damaged by the earthquake.”
This story was originally published April 1, 2020 at 8:20 AM.
