A powerful earthquake in the Caribbean caused the appearance of a series of false quake alarms in California.
Scientists with the U.S. Geological Survey said a wave of seismic energy confused computers that try to triangulate the location of earthquakes along the West Coast. It began shortly after 11 a.m., when a magnitude 7.3 earthquake struck 23 miles (37 kilometers) southeast of Roseau, the capital of Dominica, a temblor that was felt as far away as Puerto Rico.
As the wave of energy from that quake passed through California, computers initially spit out warnings that a magnitude 6.0 temblor had struck near Chico in the north-central part of the state. Seconds later, monitors indicated an arc of earthquakes stretching from San Luis Obispo on the state's central coast to Lake Tahoe.
The readings were posted automatically on the Geological Survey's Web sites.
"These were all mislocated, picking up energy coming out of the Caribbean and treating it as a local earthquake," said Bob Dollar, a geophysicist with the Geological Survey.
"All of these mythical quakes struck within a few seconds of each other, and frankly that's a clue for us that the rash didn't actually occur. The trick is you have to make sure every one of them was false."
Dollar and a team of scientists analyzed each of the reported California earthquakes and determined all were false alarms. The wave of fake quakes began registering nine minutes after the Caribbean quake.
In September, a similar incident occurred when a massive earthquake struck off the Mariana Islands in the Pacific Ocean. The quake triggered six false quakes in California.