3 Quakes Reported by State Now Called ‘Phantom’ Errors

Three minor earthquakes reported on Sunday by the state Office of Emergency Services never occurred, and the false readings were a result of static or other interference in the microwave system that links monitoring stations throughout the state to the offices of the Department of Water Resources in Sacramento, an OES spokesman said.

Such “phantom earthquakes” pop up in the system occasionally, said Paul Morrison, chief of earthquake engineering for Water Resources, but seismologists can generally distinguish genuine quakes from such noise.

Unfortunately, Morrison said, seismologists are not normally on duty over the weekend.

Larger quakes--those with a magnitude of 4 or greater--are normally also confirmed by seismologists at Caltech, UC Berkeley, or the U.S. Geological Survey, but no one was on duty at those locations either, OES spokesman Tom Mullins said.

The phantom quakes had reported magnitudes of 3.6 and 3.2 near Santa Clara at 8:17 a.m. and 8:28 a.m., respectively, and of 3.9 near Mono Lake at 7:27 a.m.

“We depend on the Department of Water Resources seismology stations to give us preliminary information about the magnitude and location of quakes,” Mullins said. “When we get that information, the warning controller calls the county and asks for estimates of damages and injuries. . . . The readings from Water Resources are used just to trigger calls to local agencies and are not considered official reports.”

OES also failed to report a magnitude 2.6 temblor that also hit Sunday near San Jose at 10:28 p.m.

“Quakes under magnitude 3 are frequently not reported, however,” Mullins said.

“In the future,” he said, “we will stress the fact that such reports are unofficial and have not been corroborated.”