Earthquake shakes small Northern N.M. town

• By Scott Wyland swyland@sfnewmexican.com
• July 12, 2021

A magnitude 4.2 earthquake near the small Northern New Mexico village of Gallina rattled nearby small towns Monday and was felt as far away as Los Alamos and Santa Fe counties, according to U.S. Geological Survey’s seismic readings.

Three tremors shook the Gallina area roughly 40 miles from Los Alamos, with the strongest measured at magnitude 4.2 at about 9:30 a.m.

Although the quake was very low-intensity when it reached Los Alamos, it prompted more than 215 people to respond through a “Did you feel it?” report the USGS provides on its website.

That dwarfs the number of responses from other areas, including those that took the brunt of the quake. Jemez Springs came in a far distant second with about 20 people reporting they felt it.

“They probably felt it for a second — like a jolt,” Don Blakeman, USGS geophysicist, said of Los Alamos respondents. “It might have scared a few people and got their attention. And I just think there are a lot of scientists who are more likely to report the earthquake than the general public.”

Lab officials said it caused no damage or disruptions at the site.

“The laboratory’s Emergency Management Organization is aware of the event and will continue to monitor the situation,” lab spokesman Peter Hyde wrote in an email.

Blakeman said the quake’s intensity at Los Alamos was too low to cause any structural damage on a house, let alone sturdy government buildings. It might knock off a precariously placed cup on a shelf, he said.

Still, one longtime critic of the lab’s nuclear weapons program said the seismic activity shouldn’t be taken lightly.

“Such a small earthquake at that distance wouldn’t pose much of a danger in Los Alamos,” said Greg Mello, executive director of the nonprofit Los Alamos Study Group. “But it serves as a reminder that the Jemez Mountains are geologically active.”

The lab’s older, Cold War-era buildings, where people still work, are fragile enough to collapse even in a moderate earthquake centered on the Pajarito fault zone, Mello said. One of the buildings that will be used to assist in producing nuclear bomb cores — or pits — is scheduled to be replaced in 2026 because it’s aging, he added.

The lab should do a thorough inspection of all its buildings to see which ones are seismically vulnerable, because even a magnitude 5 quake on the plateau could be devastating, Mello said.

The potential for earthquakes has been a factor in determining how many pits should be produced at the lab, he said.

Blakeman said small quakes like the one on Monday can happen anywhere in the lower 48 states except North Dakota and Florida.

“It’s not like we have these every day, but it’s not an unusual thing,” he said.