© U.S. Geological Survey
The series of at least three quakes generated no reports of notable damage, but left people swaying or stunned from Black Canyon City, closest to the epicenter, to Camp Verde and across metro Phoenix as far as Queen Creek.
In central Phoenix and elsewhere, the largest quake came as one quick rap - a bit like a distant explosion without the sound, or an unexpected bang on the door.
Tempe City Councilwoman Lauren Kuby lives in central Tempe near Alameda Drive and College Avenue.
"I just heard this rumble and this movement and I thought it was my dog falling off the bed," she said. "It felt like a rumble and a slight movement and then like a thud."
Norris Nordvold and his wife were up late and felt the rumble. Like others startled by earthquake, he posted on Facebook.
"I was on the couch and my wife was at the table and our house definitely moved at 11:31 p.m," he said. "We were babysitting our granddaughter ... and she woke up, too."
The quakes were centered along the Agua Fria River a few miles north of Black Canyon City, according to the U.S. Geological Survey.
Black Canyon City is located about 20 miles north of Phoenix, a community bisected by the I-17 with a population of about 2,600 people. Before the highway opened, it formerly was a settlement along the scenic main route from Phoenix to Prescott. Now, Black Canyon City is perhaps best known to Valley residents as just another name on a road sign on the drive up to Flagstaff - along with Bumble Bee, Cordes Junction and the like - as well as the home of Rock Springs Cafe. (Indeed, when news of the earthquake spread, one reader's first reaction was to "Save the pies!!!!")
Earthquakes are rare in Arizona, which is removed from the major fault lines of the West Coast. Still, Sunday night's quakes were far from the first. A 4.7-magnitude quake shook the Oak Creek Canyon fault near Sedona in December 2014, and others shook the Arizona-New Mexico border in June of that year.
Comment: Maybe not so coincidentally, there are fracking operations in the Black Canyon City area.
But perhaps the more memorable recent shaking came in 2009, when a series of powerful quakes in Baja California, ranging from magnitude 5.0 to 6.9, sent their tremors as far north as Phoenix. Those rumbles, around 11 o'clock on a Monday morning, were far easier to feel in a Valley that was up and about, at work in offices, schools and downtown towers.
Sunday night's tremors were comparatively less significant, both for their magnitude and their timing, said Zachary Reeves with the U.S. Geological Survey in Golden, Colo.
"In general, it's relatively small," he said of the 4.1-magnitude peak earthquake Sunday, the largest of the series. "If people are in bed then people may not even be woken up by it."
Still, the quakes were notable for at least two reasons beyond their simple rarity in the region.
First, the largest apparent temblor was preceded by a 3.2-magnitude foreshock, first reported at about 9 p.m.
"It's not common, but it does happen where you get small foreshock and that triggers a larger event," Reeves said. "Typically the first shock is the main one and everything after is at least a magnitude smaller. This is definitely not common."
Second, the quake hit relatively close to the Earth's surface, which may have made its effect more pronounced. Quakes are measured both in their magnitude - the power of their shaking - and their depth. Their destructive power varies with both those factors, as well as local building standards.
Sunday's largest jolt came at 6.5 kilometers - about 4 miles - beneath the surface. By comparison, the destructive Northridge earthquake in Southern California in 1994 struck at more than 18 kilometers deep.
Reeves couldn't say as of late Sunday what fault line had triggered the quakes.
The 4.1 was the largest quake recorded on continental North America on Sunday, according to the USGS, though sensors did register a 4.3 quake in the Pacific off northern California, and a 5.1 off El Salvador.
Though the Arizona shaking wasn't destructive, it was unsettling in its own way.
Kyle Greene said he was in bed in Queen Creek when the shake happened. "I had no idea what could have made a noise like that," Greene said. "I actually grabbed a gun and went out in to the front room to see what was going on."
In north Scottsdale, Mario Diaz was less stunned.
"Having lived in Los Angeles for 20 years and having gone through several earthquakes," he said, "I knew what I was feeling."
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