The San Francisco Bay Area has a 72 percent chance of experiencing a magnitude 6.7 or larger earthquake somewhere within the region before 2043, according to the U.S. Geological Survey. The estimate comes from a probability model built around the dense network of faults running beneath the Bay Area, including the Hayward, San Andreas and Calaveras faults. USGS scientists have also used a hypothetical magnitude 7.0 rupture of the Hayward Fault, centered in Oakland, as a planning scenario to study what that kind of earthquake would do to the region’s infrastructure.
Called HayWired, the scenario is not a forecast that a magnitude 7.0 earthquake will strike on any particular date. It is a scientifically grounded exercise: USGS researchers modeled ground shaking, aftershocks, fires and damage to water, power and transportation systems as if such a quake had already happened, so that emergency planners, utilities and local governments could see the cascading effects in advance rather than after the fact.
A Region-Wide Probability, Not a Single-Fault Prediction
The 72 percent figure covers the entire San Francisco Bay region and any of its faults capable of producing a magnitude 6.7 or greater earthquake, according to the USGS Earthquake Outlook for the San Francisco Bay Region, 2014-2043. It is not a probability specific to the Hayward Fault alone, a distinction that gets lost when the number circulates on its own.
The Hayward Fault by itself carries a lower individual probability, about 33 percent for a magnitude 6.7 or greater rupture in roughly that same span, according to the USGS HayWired program page. Combined with the San Andreas, Calaveras and other regional faults, the odds across the whole Bay Area rise to the 72 percent figure that anchors the HayWired scenario’s planning assumptions.
A Fault Overdue for Its Next Major Rupture
USGS singled out the Hayward Fault for its scenario partly because of history. The fault last produced a damaging earthquake in 1868, and the USGS’s own account of that quake notes the fault is “due anytime for another magnitude 6.8 to 7.0 earthquake,” a warning issued on the 150th anniversary of the 1868 rupture. That anniversary, in 2018, coincided with the release of the HayWired scenario itself. USGS points researchers to a detailed account of the 1868 quake and its aftermath, including damage photographs, preserved in a chapter of the Lawson Report, the landmark scientific investigation originally compiled after the 1906 San Francisco earthquake.
The scenario’s earthquake-hazards volume models a hypothetical magnitude 7.0 quake with its epicenter in Oakland, larger than the region-wide 72 percent threshold of magnitude 6.7, on the reasoning that planners need to prepare for a worse-than-typical event rather than the statistical minimum. Shaking of that severity beneath one of the country’s most densely built urban corridors would strain bridges, BART tunnels, older unreinforced buildings and the underground pipes that carry water and gas across the East Bay and San Francisco.
Liquefaction is a particular concern in low-lying, human-made and reclaimed land around the bay’s edge, where loose, wet soil can temporarily behave like a liquid during strong shaking. Landslides pose a separate risk in the hillier parts of Oakland, Berkeley and the Peninsula, where homes sit close to steep, fault-fractured terrain.
The HayWired project didn’t stop at ground motion. USGS assembled teams of engineers and social scientists alongside its seismologists to study cumulative aftershock impacts, how buildings built under current codes would actually perform, how interconnected infrastructure systems such as power and water depend on one another, and what separates communities that recover quickly from a disaster from those that don’t.
Estimating the Toll of the Next Big One
Beyond the Bay Area, USGS estimates that long-term annualized earthquake losses nationwide exceed $6.1 billion a year, affecting more than 143 million people who live in areas of measurable seismic hazard. That $6.1 billion figure isn’t tied to any single earthquake; it’s an annualized estimate that spreads the expected cost of seismic damage evenly across every year, the way an insurer might average out a risk that could show up as one catastrophic year or several quiet decades.
Ken Hudnut, the USGS science advisor for risk reduction who led the HayWired scenario, has said the goal is to help communities “anticipate the impacts of a hypothetical M7.0 earthquake on the Hayward Fault” well before the ground actually moves.
USGS has been explicit that HayWired describes what could happen, not what will happen on any particular day. The agency’s own language calls the scenario “not a prediction,” a distinction that matters for a region where the underlying probability, a 72 percent chance of a magnitude 6.7 or greater earthquake somewhere in the Bay Area by 2043, has stood unchanged since USGS and its partner researchers first published the analysis in 2014.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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