The report alone was enough to get newsrooms jumping Friday, not to mention Twitter.
Once it was determined the quake was a false report, UGGS turned to its Twitter account and sent the following:
It also disappeared from USGS system with the strike of a delete button.
Richard Buckmaster, a geophysicist at the USGS's National Earthquake Reporting Center, says officials are trying to determine why the computer generated the "dubious or erroneous" alert. He says the center's equipment saw no evidence that Napa had experienced even a much smaller quake.
Buckmaster says such inaccurate reports are exceedingly rare in California.
Here's how the original email appeared. They had an exact location for the shaker:
5.0 - duration magnitude (Md)
Friday, April 30, 2010 at 12:43:00 PM (PDT)
Friday, April 30, 2010 at 19:43:00 (UTC)
Napa, CA - 11 km (7 miles) NE (48 degrees)
Green Valley, CA - 13 km (8 miles) NNW (344 degrees)
Yountville, CA - 14 km (9 miles) ESE (105 degrees)
Vallejo, CA - 29 km (18 miles) N (5 degrees)
Oakland, CA - 64 km (40 miles) N (2 degrees)
Coordinates: 38 deg. 22.2 min. N (38.370N), 122 deg. 12.3 min. W (122.205W)