Yes, this was someone's idea of an April Fool's Day joke.
And the U.S. Geological Survey, which has had its hands full with the swarm of earthquakes that started Friday night in the La Habra area, isn't about to play around with stuff like this. USGS officials stated last night that a document on its letterhead warning of a 7.4 earthquake is a hoax.
See also: 5.1 Earthquake Shakes SoCal
The survey folks say, of course, that …
… they can't predict earthquakes! The closest they can come is a prototype “Shake Alert” system that gives USGS officials and very few others a very limited warning when temblors from far away are en route.
Alarms at the USGS and select other locations sound when a quake has already started and is headed to L.A. Experts wouldn't know the magnitude until the shaker actually shakes.
But a day or so warning and an exact magnitude prediction? That's science fiction. The USGS says:
USGS is aware of a letter circulating on the Internet that uses our logo and warns of an impending sizable earthquake in Southern California. USGS had no part in this letter or any alleged alert. USGS does not predict earthquakes. USGS distributes reliable and timely scientific information on earthquakes and makes it all available to the public. The message of being prepared is always valuable.
CBS Los Angeles obtained a copy of the letter, which was being circulated via email, the stations says. The document warns:
Please be advised as of this morning, March 31, 2014, the state of California is issuing a statewide warning as we have just received information from the state's Seismic Warning Systems urging residents in the following areas to be prepared for a sizable earthquake, up to, but not limiting, a 7.4-magnitude tremor.
(Note the erroneous use of tremor for temblor).
Among the cities being warned in the letter are La Habra and Long Beach. Of course, a real 7.4 would likely affect a wide swath of Southern California. In fact a 7.2 rocker that struck in the Baja California Norte, Mexico desert on April 4, 2010 was likely felt by 20 million people, experts said. People even felt it in Phoenix.
It was so far out in the remote desert, however, that only two deaths were reported, and damage was limited to mostly unpopulated areas.
A representative of Seismic Warning Systems says the letter is, in part, a “false statement being attributed to me … [and] my company … “
Because the letter also used USGS letterhead, some folks who got it thought it was, well, for real.
It's always good to be prepared for the worst. Just know when that swaying motion is just the result of people yanking your chain.