Hayward Fault: major earthquake in San Francisco could happen at anytime

July 2015 – SAN FRANCISCO – Panic has erupted throughout social media, as earlier reports stated that San Francisco will experience a major earthquake “any day now.” The story came out after a 4.0 magnitude earthquake on the Hayward Fault rocked the Bay Area on Tuesday. A U.S. Geological Survey scientist said that the fault is expected to result in a major earthquake “any day now” and advised Bay Area residents to be prepared, according to CBS San Francisco. The story quickly picked up on Facebook and became viral, spreading panic on social media and fear among the Bay Area residents. The story was apparently sourced from the local news wire Bay City News, which reported that “while a 2008 report put the probability of a 6.7-magnitude or larger earthquake on the Hayward-Rodgers Creek Fault system over the next 30 years at 31 percent, Brocher said the reality is a major quake is expected on the fault ‘any day now,’” SF Gate reported.

Tom Brocher, research geophysicist at the USGS Earthquake Science Center, set the record straight and clarified that a major earthquake can hit the Bay Area at any time, not any day now, as there is still no way to accurately predict when earthquakes will occur. “The Hayward fault is capable of producing a major earthquake at any time, but there is currently no scientific basis for making a prediction for when that earthquake will occur,” Brocher said. Brocher said the Uniform California Earthquake Rupture Forecast model has predicted that a magnitude 6.7 earthquake or greater may occur in 30 years along the Hayward-Rodgers Creek fault system. The model’s prediction is at 31 percent probability.

Bay City News corrected its report, at Brocher’s request, to read “Although the fault that produced a 4.0-magnitude earthquake in Fremont this morning is not expected to change the likelihood of another major quake on the same fault, a U.S. Geological Survey scientist said a major earthquake could happen at any time and residents should be prepared,” according to SF Gate. The last earthquake on the Hayward Fault occurred on Oct. 21, 1868 with a 6.8 magnitude. It was one of the most destructive quakes in the history of California, even though the Bay Area at the time was not as densely populated as it is today. Scientists said in a 2008 USGS Fact Sheet that the fault is “a tectonic time bomb, due anytime for another magnitude 6.8 to 7.0 earthquake.” –HNGN