MENLO PARK, Calif. (KTVU) -- Three false earthquakes reported in the Bay Area over the weekend were actually false readings of seismic energy from two real quakes; a 6.7 magnitude quake in Alaska on Friday, and a 7.8 magnitude in Japan on Saturday.
"It fooled our automatic earthquake processing system into thinking these waves were caused by one or more local earthquakes," explained U.S. Geological Survey seismologist, Lind Gee.
"The problem with phantom earthquakes is greater with deep earthquakes," Gee said. "The fact that we had one false event on Friday and two on Saturday is a bit of a coincidence."
Gee was the seismologist on duty when the earthquake sensor system detected energy from the large distant quakes, interpreted them as moderate local quakes, and sent out automatic alerts.
"So your heart is racing," Gee said recalling looking at the data. "And as soon as I looked at the events, I was like, 'Oh no!'"
For 15 to 20 years, seismologists have been working on a better system to decipher large distant quakes, from so-called phantom quakes.
"We've put software into place to identify and screen these phantom earthquakes before they're publicly distributed," but Gee said that software needs to be tweaked to filter out false quakes like the ones this past weekend.
"It's an active area of research," she said. "We expect to learn a lot from these two false events Friday and Saturday that will help us improve the system operations to minimize these false alarms."
Another software glitch prevented Gee's correction of the reported earthquake from reaching those who subscribe to earthquake alerts via text or email. On Monday evening the USGS reported that software problem had been fixed.
"So this is part of the challenge between reliability and getting information out quickly," Gee said the USGS's emphasis is on speed to help emergency first responders react quickly to save lives. "But the cost of that is sometimes we're wrong."
For all the advances in earthquake science, it isn't a perfect science. It still relies on people to keep computers in check.
"It's fair to say the Earth can always throw us a surprise," Gee said with a grin.