HayWired: A Magnitude-7.0 Earthquake Scenario for the Hayward Fault

The HayWired earthquake scenario, led by the U.S. Geological Survey (USGS), imagines a hypothetical magnitude 7.0 earthquake on the Hayward Fault, along the east side of San Francisco Bay — one of the most active and dangerous faults in the U.S., because it runs through a dense, interconnected urban region. A realistic scenario is a way to learn about a big earthquake without living through one.

The name joins the Hayward Fault with the region's wired interdependence — people, utilities, roads and the digital economy. It is one plausible next "big one" among many, built to guide residents and policymakers toward actions that cut injuries, damage, displacement and recovery time. The first report appeared in April 2017 (Scientific Investigations Report 2017–5013). The motto: "Together, we can outsmart disaster!"

A certain future

• History: major prehistoric earthquakes struck the Hayward Fault roughly every 100 to 220 years over the past 1,900 years. For the last 12, the average interval was about 150 years, plus or minus 60.
• The last one: a magnitude 6.8 in 1868 — 150 years before this fact sheet.

Damage from the 1868 Hayward Fault earthquake. California State Library.

The scenario earthquake

• When and where: 4:18 p.m., April 18, 2018 — the anniversary of the M 7.8 1906 San Francisco earthquake — beneath Oakland.
• Rupture: about 52 miles of the fault.
• Hardest hit: the corridor from Richmond to Fremont, including Berkeley, Oakland, San Leandro and Hayward — violent shaking and sudden fault offset, more than 6 feet in places, with slow afterslip for months.
• Across the region: strong shaking; liquefaction of wet, sandy soils along the bay and streams; landslides in the hills, especially the East Bay.
• Aftershocks: for minutes to years afterward; the largest, M 6.4, in Santa Clara County near San Jose.

Simulated shaking from the scenario mainshock. Red is the most extreme shaking and worst damage; the star marks the start beneath Oakland, the thick line the roughly 52-mile rupture. USGS.

Buildings

• The fault runs beneath more than 300 buildings and structures — UC Berkeley's Memorial Stadium is nearly cut in two by it and has been retrofitted. About 2 million buildings in the region are at risk.
• Losses: more than $82 billion (2016 dollars) in property damage and direct business disruption — mostly from shaking, then liquefaction, then landslides. Eighty percent of shaking damage comes from the mainshock, the rest from 2 years of aftershocks.
• Downtowns: older steel-frame high-rises and newer reinforced-concrete residential buildings in Oakland and San Francisco could be unusable for up to 10 months.
• Displacement: about 77,000 households, or with utility outages as many as 152,000 — roughly 411,000 people.
• Even at current code: 0.4 percent of buildings could collapse, 5 percent be unsafe to occupy, and 19 percent have restricted use.
• Better codes: for a small added cost, stronger buildings could let 95 percent of people stay in their homes and workplaces — and the public, asked, says it would pay for that.

Casualties

• 800 deaths and 18,000 nonfatal injuries from building damage, shaking and liquefaction.
• More than 2,500 people needing rescue from collapsed buildings, and more than 22,000 from stalled elevators.
• With ShakeAlert early warning fully running and people doing "Drop, Cover, and Hold On", as many as 1,500 of those injuries could be prevented.

Water

Old, brittle pipes break in big earthquakes, and repair depends on other utilities, roads, labor and materials. A new water-network model estimates most of the region would be hit, and East Bay residents could lose water for 6 weeks — some for 6 months — also crippling firefighting.

Water-service restoration by county, now (left) and if utilities replaced all brittle pipe and had fuel plans and generators at every pumping station (right). USGS.

Fire

• More than 400 gas- and electric-related fires could ignite, possibly merging into conflagrations as destructive as the shaking. (The 1991 East Bay Hills firestorm killed 25 people, destroyed more than 3,000 homes and 450 apartment units, and burned more than 1,500 acres.)
• With too few firefighters and trucks — slowed by communication outages, blocked roads and water shortages — building space equal to more than 52,000 single-family homes could burn, killing hundreds and adding losses near $30 billion.
• Seismic retrofits reduce ignitions. A 2014 workshop with firefighters stressed coordination with water utilities, and led to the first joint exercise of portable firefighting water systems.

Still being studied

Effects on information and communications technology (the "wired" — Silicon Valley matters to the national economy); lifelines such as highways, BART, telecommunications and power, and how they depend on each other; community recovery — displacement, social vulnerability, housing and financing; jobs and the economy; and the benefits of ShakeAlert.

New science behind it

• Hazards: computer-simulated seismic waves for shaking; probabilities of landslides and liquefaction; plans to communicate aftershock forecasts; projections of continued fault offset.
• Damage: buildings, including extra damage from aftershocks; water networks and interdependent lifelines; fire; people trapped.
• Risk reduction: replacing brittle pipes and a backup fuel plan restore water faster; stronger codes cut damage to new buildings; the public expects buildings to be usable afterward; ShakeAlert plus drills could prevent thousands of injuries.

Investing in safety

The 1868, 1906 and M 6.9 1989 Loma Prieta earthquakes spurred action. In the nearly 30 years since Loma Prieta, the region has invested at least $25 billion, possibly $50 billion, in earthquake countermeasures, and cities and utilities tens of billions in upgrades, retrofits and replacements. HayWired shows there is more to do.

Coalition and campaign

• HayWired Coalition: since 2014 USGS has worked with 80 fire chiefs, dozens of emergency managers, and utilities, transportation agencies and the IT industry; from 2016 this became a coalition of more than 50 agencies and businesses. Members have used the scenario to explore shaking simulations, stricter-code trade-offs, lifeline interdependencies, a toxic plume exercise with hospitals, IT resilience, business recovery plans, city recovery challenges, and housing policy.
• HayWired Campaign: led by the California Seismic Safety Commission and the California Business, Consumer Services, and Housing Agency, at Outsmart Disaster.

More: the HayWired geonarrative · the 1868 Hayward earthquake · Is the Hayward Fault due for a repeat? · Seven Steps to Earthquake Safety

Sources

Based on The HayWired Earthquake Scenario—We Can Outsmart Disaster, U.S. Geological Survey Fact Sheet 2018–3016 (publication page), by Kenneth W. Hudnut, Anne M. Wein, Dale A. Cox, Keith A. Porter, Laurie A. Johnson, Suzanne C. Perry, Jennifer L. Bruce and Drew LaPointe. The shaking map and water infographic are restored from its PDF, with the 1868 photograph (California State Library), which is in the public domain. Two maps on licensed commercial base images, a diagram built with third-party silhouettes and a company's photograph are left out. A work of the United States government in the public domain.