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Earthquake In LA? Nope, That Was A Sonic Boom That Rattled Your Home’s Windows This AM

A grayscale overview map of Southern California has a grud of light blue and lavender squares indicating where people felt shaking, largely concentrated around Long Beach.
A US Geological Survey assessment concluded the sonic boom originated in San Dimas.
(Screenshot courtesy USGS)
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At about 9 a.m. Friday, people living between West Covina, Long Beach, and Santa Monica felt shaking. L.A. earthquake Twitter came to life, per usual. But check the USGS’s Latest Earthquakes list, and you’ll see that there’s no quake to be found.

That’s because it wasn’t an earthquake, but a sonic boom originating in San Dimas, according to an assessment from the USGS.

Sonic booms occur when aircrafts exceed the speed of sound — some 760 mph at sea level. As they move faster and faster, the planes violently push air molecules out of the way, creating shockwaves that can take as much as 60 seconds to be heard on the ground.

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Edwards Air Force Base is close by and it happens to have an entire page about noisy flyovers and sonic booms, though it has not yet confirmed or denied that that's what happened Friday morning.

One Twitter sleuth pointed out that this weekend there’ll be F-18s flying out of the Long Beach airport for training.

Even though it wasn’t a quake, now’s still a good time to prepare for one.

What do you want to know about fires, earthquakes, climate change or any science-related topics?
Jacob Margolis helps Southern Californians understand the science shaping our imperfect paradise and gets us prepared for what’s next.