A landmark report in 2018 by the U.S. Geological Survey estimated that at least 800 people could be killed and 18,000 others injured in a hypothetical magnitude 7 earthquake rupturing on the Hayward fault through Oakland, Berkeley, Richmond, Hayward and Fremont.

Hundreds more could die from fire following an earthquake along the ruptured 52-mile section of the fault in this HayWired scenario. More than 400 fires could ignite, burning the equivalent of 52,000 single-family homes, and a lack of water for firefighters caused by old pipes shattering underground could make matters worse, USGS geophysicist Ken Hudnut has said.

“This fault is what we sort of call a tectonic time bomb,” USGS earthquake geologist emeritus David Schwartz said of the Hayward fault. “It’s just waiting to go off.”

The Hayward fault is so dangerous because it runs through some of the most heavily populated parts of the Bay Area, spanning the length of the East Bay from San Pablo Bay to Milpitas.

Out of the region’s population of 7 million, 2 million people live on top of the fault.

In this Oct. 17, 1989, photo, a California Highway Patrol officer checks the damage to cars that fell when the upper deck of the Bay Bridge collapsed onto the lower deck during the Loma Prieta earthquake. (George Nikitin / Associated Press)


The so-called HayWired scenario envisions a scale of disaster not seen in modern California history — 2,500 people needing rescue from collapsed buildings and 22,000 being trapped in elevators, Hudnut said. More than 400,000 people could be displaced from their homes, and some East Bay residents may lose access to clean water for as long as six months.

The earthquake would cause 8,000 structures to collapse, 100,000 to be red-tagged — meaning they’re too damaged to enter — and 390,000 to be yellow-tagged, meaning occupancy is limited due to significant damage, Keith Porter, a University of Colorado Boulder research professor who coordinated the HayWired report’s engineering section, has said.