The HayWired Earthquake Scenario: What a Magnitude 7.0 on the Hayward Fault Would Do

Census tracts with concentrated damage in the HayWired scenario — at least 20 percent of building floor area extensively or completely damaged. Yellow tracts are damaged by the earthquake; orange tracts join them once fire is counted. Green is preserved land. U.S. Geological Survey.

A realistic earthquake, before it happens

The HayWired scenario, led by the U.S. Geological Survey (USGS), works through the likely effects of a hypothetical magnitude 7.0 earthquake on the Hayward Fault — one of many plausible candidates for the San Francisco Bay region's next big one. The name points to the Hayward Fault and to the region's interconnection: its people, utilities, telecommunications, roads and digital economy. With partners in the HayWired Coalition, USGS uses it to spur residents and businesses to prepare.

• The fault: runs along the east bay, among the most active and dangerous in the country, through a dense region of more than 7 million people.
• The rupture: shifts the two sides up to 2.1 meters (about 6 feet); where the first slip was smaller, another 0.5–1.5 meters builds up, ever more slowly, over days to years. Aftershocks go on for 2 years.
• The shaking: damaging (Modified Mercalli Intensity VI or more) across the nine counties around the bay and Santa Cruz County. It liquefies wet, sandy soil along the bay and streams, and sets off landslides, especially in the east bay hills.
• The damage: shaking and fires damage buildings, and where damage concentrates, neighborhoods and business districts can be disrupted.

Acting now can save lives and well-being, keep buildings and infrastructure working, keep people in their homes and businesses open, and shorten recovery.

People affected by concentrated building damage from earthquake and fire, from origin-destination data in the Longitudinal Employer-Household Dynamics database (2015). U.S. Geological Survey.

Phones and internet

• Hundreds of fiber-optic cables cross the fault.
• Shaking, liquefaction and fire hit cell sites on buildings and poles, central offices and emergency call centers; data centers on liquefaction-prone ground take the cumulative toll of the aftershocks.
• Power outages, more than damage, knock equipment out. Backup power lasts hours to a few days; portable equipment and fuel face short supply, labor shortages and blocked sites, which may delay restoration by days to weeks. Poorly maintained batteries wear down through the aftershocks.
• Demand jams the networks: fewer calls get through, data slows, and lost calls compromise 9-1-1, including reports of fires — just as people with critical communication needs, social vulnerabilities or access needs are evacuating.

After the earthquake:

Lifelines tangled together

Transportation, energy, telecommunications and water all face multiple hazards — widespread shaking, liquefaction, landslides and fires. Long-haul fiber is more exposed than roads, water lines and pipelines. Systems that run side by side (collocated) share collateral damage and depend on one another for repairs. Local roads and fiber lines often run together, but collocated highways, railways, gas and petroleum pipelines and high-voltage power lines may deserve priority to protect or harden beforehand and restore afterward. Critical collocated infrastructure is exposed near the Port of Oakland, San Francisco International Airport and dense neighborhoods; mapping these places could help providers plan and exercise together.

Earthquake hazards and collocated lifelines in three areas. USGS; icons from the UN Office for the Coordination of Humanitarian Affairs (CC BY 4.0).

Restoration: telecommunications, though hit hardest at first, come back fastest — days to weeks. Fuel takes at least 10 days, electric power weeks, gas, water and highway bridges months, and some BART stations in the east bay years.

Communities at risk

Hundreds of thousands of people could be displaced — by uninhabitable homes or neighborhoods, or by lost services nearby. The communities most at risk combine concentrated damage (the 20 percent threshold, drawn from past earthquakes) with social and economic vulnerability. Racially and culturally diverse and socially vulnerable people are hit disproportionately: renters, people with high housing costs or low incomes, and people with little schooling or English face a higher risk of displacement and a harder recovery.

Places where utilities and transport are slow to return, or where the ground liquefies, slides or keeps slipping along the fault, face long recoveries. The region already has a housing shortage and many unretrofitted buildings; local governments will need to plan for housing the displaced and for financing the repair and rebuilding of 1.37 million housing units.

The economy

• Output: in the first 6 months, damage, outages and supply-chain ripples cost $44 billion of gross state product — 4 percent of California's economy. Business continuity and resilience measures — restoring service faster (a portable cell site), switching suppliers, conserving water, catching up with overtime — can cut that by 40 percent, to $25 billion.
• Commutes: on the Peninsula and in the south bay, broken commutes cost more jobs than damaged buildings — though the analysis assumed less teleworking than the COVID-19 pandemic brought.
• Jobs: recovering from a recession of almost half a million lost jobs takes a few years, but returning to the forecast path could take more than 5 years for the region and close to a decade for the hardest-hit places, such as Alameda County. Rebuilding helps; shortages of construction workers, soaring costs and big businesses leaving would slow it.
• Businesses: damaged buildings interrupt about 8 percent of the region's establishments and workers — 40 percent in central Alameda County — and industrial and warehouse sites suffer disproportionately. More than half a million workers (14 percent) lose access to work, their homes, or local services.

Seconds of warning

Most preparation happens in advance — building codes and plans. The last chance comes in the seconds before strong shaking, when automated or self-protective actions can cut injuries, network load and demands on search and rescue. ShakeAlert® earthquake early warning went public on the West Coast while HayWired was being developed, and the scenario helps imagine its use through an aftershock sequence and at every stage of response and recovery.

Money well spent

In the 30 years since the Loma Prieta earthquake, the region has invested about $80 billion (in 2016 dollars) in seismic strengthening — transportation, water and other critical systems; hospitals, schools and government buildings; unreinforced masonry, soft-story and other vulnerable buildings. Because business interruption comes mainly from building damage and transportation, those upgrades have likely reduced future losses. Per person, San Francisco has invested more than four times as much as the harder-hit Alameda, Contra Costa and Santa Clara Counties. More remains: vulnerable buildings, water distribution, BART stations and fuel supplies.

What participants call for

1. Cities coordinating response with one another, power companies, carriers, emergency managers and amateur radio operators.
2. A regional lifeline council of providers and emergency managers.
3. Investment in infrastructure, with businesses in mitigation planning.
4. Recovery planning with community groups, including properties in hazardous places, displacement, temporary housing, rebuilding affordable housing stronger, faster permits and funding, and room for new ideas.
5. Lessons from COVID-19 and wildfires, for fair outcomes.

The coalition

Since 2014, USGS has worked on HayWired with Bay Area organizations — including 80 fire chiefs, 25 emergency managers, and utilities, transport agencies and the tech industry. From 2016 the HayWired Coalition, now more than 50 agencies and businesses, has carried the scenario to their communities, to build capacity, advance knowledge, inform risk reduction and put hazard science to use. It has shaped the state's Outsmart Disaster campaign, regional planning, response and business-continuity exercises, the ShakeOut drills, a business exercise toolkit, a study of electrification after an earthquake, and research on how sea-level rise changes liquefaction.

After the pandemic

Like COVID-19, a HayWired earthquake strikes suddenly, supplies must move fast, supply chains falter and workplaces change. But only the Bay Area would be hit, and sheltering and working in place, which served well in the pandemic, would be far harder amid physical damage and outages. The pandemic also showed how the digital divide would make response and recovery unequal. Mitigation, stockpiles and plans for fair recovery could reduce suffering — and pandemic stimulus could fund infrastructure that also resists earthquakes and fire.

More: the full scenario, volumes 1 (2017) and 2 (2018); the HayWired geonarrative; the 1868 Hayward Fault earthquake; Seven Steps to Earthquake Safety.

Sources

Based on The HayWired Earthquake Scenario—Societal Consequences, U.S. Geological Survey Fact Sheet 2021–3054, by Anne M. Wein, Jamie L. Jones and Dale A. Cox of USGS with Laurie A. Johnson, Cynthia Kroll, Jennifer Strauss and David Witkowski, USGS Publications Warehouse; published by the U.S. Geological Survey and in the public domain; rewritten in hubnx's own words. Figures recovered from the fact sheet's PDF; a photograph credited by name only is not reproduced.