Earthquake aftershock felt in Boise late Monday night, 8 recorded in last 24 hours
A magnitude-4.1 aftershock to last month’s big earthquake could be felt by some Boise residents late Monday just before midnight, according to the U.S. Geological Survey.
The epicenter was 20 miles northwest of Stanley. The shake is one of eight reported aftershocks in Idaho with a magnitude of 2.5 or higher recorded by the USGS in the past 24 hours.
Aftershocks have rattled Idaho since a magnitude-6.5 earthquake hit the region March 31. The epicenter was determined to be in the mountains northwest of Stanley and 45 miles west of Challis.
That earthquake could be felt throughout the West, with reports that it stretched to Washington, Utah and Montana. The shake caused avalanches in the Sawtooths, as well as damage to buildings in Custer County.
Within 24 hours after the initial earthquake, the USGS reported 67 aftershocks throughout the state. In total, 479 aftershocks of 2.0 magnitude or higher have been recorded since the March 31 earthquake.
The Tuesday aftershock was not the first one felt in Boise. Three days after the large earthquake hit Idaho, a magnitude-4.3 aftershock could be felt throughout the state.
Andrew Michael, a geophysicist with the USGS, told the Statesman that aftershocks like the one felt Monday night are common and can continue to occur.
“For an earthquake like this, it’s possible to have an aftershock a year later,” Michael said.
Michael said the probability of aftershocks will go down over time, but it often remains a possibility. The USGS keeps aftershock forecasts current for shakes like the one Idaho experienced. Those forecasts show the probability of aftershocks over time in terms of strength. For Idaho’s probability, the forecast shows there is a low chance of a larger aftershock.
The March earthquake was among the largest in Idaho’s history, with only the Borah Peak earthquake of 1983 registering as a stronger shake. That earthquake measured 6.9, and it killed two people in Challis near the epicenter.
This story was originally published April 21, 2020 at 11:36 AM.
