An earthquake in central Idaho was felt by many in the Treasure Valley and beyond on Monday morning.

The magnitude 4.2 quake centered near the tiny town of Clayton, about 33 miles east of Stanley and 24 miles southwest of Challis in the Salmon-Challis National Forest, struck at 9:32 a.m., according to the United States Geological Survey (USGS). It’s the largest earthquake in Idaho since Feb. 26, 2024, when a magnitude 4.9 tremor whose epicenter was in Smiths Ferry rattled the valley.

Hundreds of social media comments about Monday’s quake signaled that people in Boise, Caldwell, Eagle, Emmett, Garden City, Horseshoe Bend, Idaho City, Meridian, Mountain Home, Star and more felt the earthquake’s effects.

There have been 27 earthquakes to register at magnitude 4.0 or higher in Idaho since the start of 2020 — the most notable being a magnitude 6.5 quake on March 31, 2020, that was felt across the state.

Kaylina Colson-Casebolt, a first-year student at Boise State University, was in her dorm room on the fourth floor of Towers Hall on Monday morning when her bed started shaking, lights and blinds began swinging and items on her desk were rattling, she told the Idaho Press. None of Colson-Casebolt’s belongings were damaged, she said, adding that on a 1-10 scale, the shaking she felt ranked as a 4.5 or 5.

“Aside from being startled and confused at first, I wasn’t overly concerned as it wasn’t severe,” Colson-Casebolt said. The student also noted that her bed is “extremely solid” and that she was sitting on it while it was pushed up against a wall when it began moving.

Experiences were varied, however; multiple businesses in Stanley and Challis, close to the epicenter, told the Idaho Press that they were only aware of the earthquake because of social media and journalists contacting them seeking firsthand accounts.

The sheriff’s office in Custer County, home to Stanley, Challis and Clayton, said they hadn’t received any reports of injuries or damaged property as of Monday afternoon.

The USGS uses the Modified Mercalli Intensity Scale (MMI) to measure earthquake intensity on a Roman numeral scale from I-X, with intensities ranging from imperceptible shaking to catastrophic destruction.

Rather than measuring earthquakes on a mathematical basis — as a seismograph does — the MMI scale relies on public reports and is an “arbitrary ranking based on observed effects” such as people being awakened, furniture being moved or structures being damaged, the USGS website said.

Reports on Monday’s quake came in from across the state from as far south as east of Gooding to as far north as the south end of Coeur d’Alene National Forest. Individuals most commonly reported the quake as having weak shaking, a level II or III on the MMI scale. The majority of reports stemmed from Boise, as is expected given the city’s higher population density compared to areas nearer to the quake.

In the area around downtown Boise — about 94 miles from the quake’s epicenter — 110 individuals reported the earthquake as a III on the MMI scale. This intensity brings weak shaking that can be felt noticeably by people indoors — especially those on the upper floors of buildings — with vibrations “similar to the passing of a truck.” Many people fail to recognize earthquakes at this intensity, the website said.

Two reports near the epicenter of the quake — located north of the Sawtooth Mountains — rated the quake’s intensity as high as V, defined as moderate shaking on the scale. At this intensity level, a quake can be felt by “nearly everyone” and can jolt many awake. Dishes and windows can break, unstable objects can be overturned and households with pendulum clocks may need to restart their timekeeper, the website said.