Series of small quakes quiver beneath Yellowstone Lake. The area gets thousands a year

A series of more than 60 small earthquakes hit under Yellowstone Lake in northwestern Montana near the Idaho border the morning of Tuesday, March 29, seismologists say.

That may sound like quite a few quakes, but it’s actually normal for the area, according to the U.S. Geological Survey.

It’s one of the most seismically active areas in the country, experiencing an average of 1,500 to 2,500 earthquakes each year. They hit in swarms more than half the time, and the vast majority of those are too small for people to even feel, USGS said in a post on its website.

That was the case for the Tuesday morning cluster, which only one person reported feeling on the USGS website. The highest magnitude quake in the cluster were reported at a 3.7 magnitude. Only one other quake was above a 3.0 magnitude at 3.1, the University of Utah Seismograph Stations said in a March 29 news release.

Magnitude measures the energy released at the source of the earthquake, the U.S. Geological Survey says. It replaces the old Richter scale.

Quakes between 2.5 and 5.4 magnitude are often felt but rarely cause much damage, according to Michigan Tech. Quakes below 2.5 magnitude are seldom felt by most people.

Because earthquakes are so common in Yellowstone National Park, The University of Utah Seismograph Stations operates a network of 50 seismometers to track all that earthquake data, according to the entry on the USGS website.

There have been 48,000 earthquakes in the region since 1973, and more than 99% of those have been magnitude 2 or below and weren’t felt by anyone, the USGS entry says.

They’re most common from east to west between Hebgen Lake and the Norris Geyser Basin. Most swarms have between 10 and 20 earthquakes and can last one or two days.

“However, large swarms that can contain 1,000’s of earthquakes and last for months do occur on occasion,” the post says.

What to do in an earthquake

Earthquakes’ sudden, rapid shaking can cause fires, tsunamis, landslides or avalanches. They can happen anywhere, but they’re most common in Alaska, California, Hawaii, Oregon, Puerto Rico and Washington, according to the Department of Homeland Security.

If an earthquake strikes, it’s best to protect yourself right away. Here are tips from experts:

• If you’re in a car: Pull over and stop. Set your parking brake.

• If you’re in bed: Turn face-down and cover your head with a pillow.

• If you’re outdoors: Stay away from buildings. Don’t go inside.

• If you’re inside: Stay and don’t run outdoors. Stay away from doorways.

The best way to protect yourself during an earthquake is to drop, cover and hold on, officials say.

“Wherever you are, drop down to your hands and knees and hold onto something sturdy,” officials say. “If you’re using a wheelchair or walker with a seat, make sure your wheels are locked and remain seated until the shaking stops.”

Be sure to cover your head and neck with your arms, and crawl under a sturdy table if possible. If no shelter is available, crawl to an interior wall away from windows.

Once under a table, officials say you should hold on with one hand and be ready to move with it.

“There can be serious hazards after an earthquake, such as damage to the building, leaking gas and water lines, or downed power lines,” officials say. “Expect aftershocks to follow the main shock of an earthquake. Be ready to Drop, Cover, and Hold On if you feel an aftershock.”

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