The magnitude 6.5 quake (blue dot) occurred Tuesday afternoon about 15 miles north of Stanley, Idaho. This map shows more than 40 aftershocks of magnitude 3 or greater occurred by 2 p.m. April 1.

ENTERPRISE — Subtle tremors Tuesday afternoon from a 6.5 magnitude earthquake about 15 miles north of Stanley, Idaho, rumbled through Northeast Oregon.

“I was sitting at my computer writing,” said Alder Slope rancher Shirley Parker in her Facebook post, “when I felt sort of swaying. The rollers on my chair seemed to be moving. I looked up and the curtains were swaying.”

At the Chieftain office in Enterprise, employees felt a swaying motion that lasted for several seconds, and the blinds moved back and forth slightly. Residents of Baker City and La Grande also reported feeling the quake.

The quake occurred at about 4:55 p.m. about 115 miles southeast of Enterprise and 135 miles from Baker City. The focus was about 6 miles beneath the surface. The main shock was followed by at least 40 aftershocks of 3.0 or greater, including an aftershock of 4.6 from the same site as the original quake.

Because the quake was centered in a sparsely settled area, no structural damage has been reported, although structures in and around Stanley may have sustained damage. It also apparently caused no landslides or other natural damage of any consequence. But it shook Boise, Stanley and McCall, Idaho, significantly.

The local rumblings were about a magnitude 2 or 3, according to the U.S. Geological Survey’s intensity maps.

The quake likely occurred on the Sawtooth or Trans-Challis faults. While central Idaho might seem tectonically stable, the Challis, Idaho, area is no stranger to large quakes. These faults can unleash significant earthquakes, including the 7.3 Borah Peak quake in 1983 that killed four people and caused an estimated $12.5 million in damage.

The Wallowa Fault, with a vertical offset of more than 7,000 feet, provides magnitude 2 and 3 quakes every few years. The last magnitude 3.4 quake centered 4 miles east-southeast of Joseph in November 2014. The Baker and La Grande areas also experience similar small quakes.