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False reports of California earthquakes are caused by Russian temblor

August 14, 2012 |  7:00 am

10-degree map showing recent earthquakes

A magnitude 7.7 earthquake in a sea off the coast of eastern Russia did not cause any reported damage or injuries.

But it did cause numerous "false positive" reports of earthquakes in California, a U.S. Geological Survey official said Monday night.

The temblor struck Monday night PDT (1 p.m. local time) under the Sea of Okhotsk. Officials said it was 373 miles below ground and did not result in any tsunamis.

But for reasons that are not entirely clear, it triggered several erroneous reports of quakes in California.

Leslie Gordon, USGS spokeswoman in Menlo Park, said the false reports of earthquakes in Gerber, the Monterey area and Gilroy were triggered by the Russian quake. Those reports were retracted within minutes, Gordon said. A couple of the reports were erroneously reissued, then retracted again.

False reports occasionally are registered by USGS automatic earthquake sensors, she said.

Those sensor reports are automatically transmitted to subscribers of the agency’s earthquake notification system. Within minutes, seismologists review every report and retract those few that are false, Gordon said.

“On rare occasions we’ll have these false positives," she said. "We figure that the risk is worth it.”

The other option, she said, is to hold each earthquake report until a seismologist reviews it.

“We don’t want to hold up every single notice until it’s reviewed by a seismologist. It would add 10, 20 minutes to every notice,” she said.


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Image: Location of Russian earthquake. Credit: USGS