Shake and Bake
Update: UC Berkeley seismologists just published data proving that the Hayward Fault is essentially a branch of the Calaveras Fault—meaning that both could rupture together, generating a more devastating earthquake than the predicted “Big One.” And we thought we were envisioning the worst with this article from our apocalyptic Summer 2014 issue.
It’s late on a dry, gusty Friday afternoon in October. As the workday winds down, thoughts are drifting to the weekend, when suddenly, all across the Bay Area, people stop and exchange glances. Before they can even speak, the thought registers: Earthquake!
As the shaking grows from the first unsettling jolt, people hurl themselves under desks or tables. A low rumbling sound builds to a roar. The Hayward Fault is rupturing along its length, from Fremont to San Pablo Bay.
For 22 seconds—eternity, it seems—the shaking continues. Windows shatter, car alarms blare, people scream. Whole buildings tremble and sway. Some collapse.
In the East Bay Hills, older homes lurch off their foundations, severing gas and water connections. Trees and rocks perched on steep slopes crash into narrow winding roads below. In the flat, open areas ringing the bay, people take out their smartphones to record the strange sight of water gushing out of the ground. All across the region, traffic grinds to a halt.
Over the next few hours, callers attempting to report emergencies or check on loved ones overwhelm communications systems. Fire trucks and ambulances weave through the gridlock. In San Francisco, some 160,000 commuters are stranded and desperate to find a way home.
As the sun begins to set, the orange glow of fires can be seen around the bay. People from miles around stare in silence as a huge fire climbs the eastern hills, where drought has turned the vegetation to kindling and Diablo winds whip the flames to a frenzy.
No one wants to think about catastrophe, let alone worst-case scenarios, which the above is not. For worse, consider the Delta Doomsday scenario at the heart of late journalist Marc Reisner’s 2003 book, A Dangerous Place (think levee collapse, seriously disrupting a major supply of freshwater for two-thirds of the state’s population). Or the one put forward by late UC Berkeley geologist Garniss Curtis, who feared that in wet conditions a major seismic event on the Hayward Fault could trigger a massive landslide that would undermine the Berkeley Lab and bury a large part of the University of California’s campus. (Although Reisner’s scenario is considered a possibility, most experts dismiss the Curtis megaslide as unsupported by the known geology of the area.)
In truth, there are any number of possible outcomes of a large Bay Area earthquake, an endless series of if-then scenarios, each one contingent upon a combination of factors, including our level of preparedness. Perhaps only one thing is certain: The Bay Area is due—some would say overdue—for a major quake.
The fracture that inspires much of the concern is the Hayward Fault, which famously cuts through Cal’s Memorial Stadium. Like a winning kickoff return, it runs from end zone to end zone. For years, public safety experts feared what might happen if a quake hit on game day.
Newly remodeled to address the seismic challenge, the stadium structure is now divided into separate blocks engineered to move independently in the case of a large quake; the massive press box that seems to float above the seats can sway up to a foot during the shaking. The stage of the Greek Theatre has also been shored up with new piers and reinforced concrete columns. Before construction, the structures had seismic performance ratings of “poor” (for the stadium) and “very poor” (for the Greek).
This is the good news: Year over year, the campus has been made, if not entirely safe, at least safer. A 1997 review found that 27 percent of campus buildings by total square footage needed retrofit or seismic upgrades. Today, roughly 75 percent of that has been retrofit or replaced. “We’ve invested a lot and made great progress and have overall facilities that are safer,” says Facilities Services communications director Christine Shaff, who notes there are currently no “very poor” buildings occupied on campus. At the same time, she acknowledges, “we’re not all there yet,” and laments that a lack of state funding has slowed the pace of seismic upgrades.
There is still a lot of work to be done. The list of buildings on the UC Berkeley campus still rated “poor” includes Tolman Hall, Gianinni Hall, and Davis Hall. The latter, ironically, houses the Pacific Earthquake Engineering Research Center headquarters. Buildings rated poor are “expected to sustain significant structural and nonstructural damage and/or result in falling hazards in a major seismic disturbance, representing appreciable life hazards.”
What constitutes a major seismic disturbance? Planning scenarios typically put a large quake in the range of magnitude 6.8 to 7. This is based in part on the last big earthquake on the Hayward Fault, an 1868 event estimated to have been around 6.8. It’s possible that if the Hayward interacts with a fault like the nearby Rodgers Creek to the north, the resulting temblor might register closer to a 7.2 on the logarithmic scale used to express the magnitude of earthquakes.
It’s awful to consider the damage that might cause. The 1868 quake killed some 30 people, mostly from building collapse. But at that time Oakland was a town of 12,000 and there were only about 260,000 people living in the entire Bay Area; now there are more than 7 million, more than 2 million of whom live on or near the fault.
Public infrastructure is obviously a major concern, but many experts worry more about privately owned buildings, particularly houses. “That’s the arena that needs the most work—the private sector, both commercial and residential,” says Janiele Maffei, a Cal alum and chief mitigation officer of the California Earthquake Authority. According to projections from the Association of Bay Area Governments (ABAG), more than 150,000 housing units could be rendered uninhabitable following a large Hayward Fault quake.
Engineers are particularly concerned about older “soft-story” buildings—apartment buildings with ground-level parking spaces underneath the residences—some of which collapsed in the 1989 Loma Prieta and 1994 Northridge quakes. Other factors, including slope angle and construction type, can increase susceptibility to damage. For example, many older homes built on the slopes of the East Bay Hills, if not adequately bolted to their foundations or lacking adequate cripple wall bracing, could be seriously damaged in an earthquake.
Even properly retrofit buildings are only as safe as the ground beneath their foundations. In the hills, residents will have to contend with landslides, especially if the ground is soaked with winter rain. Many homes in the lowland areas closer to the Bay may experience violent shaking, as relatively soft alluvial soils can amplify the shockwaves from the quake. Some low-lying areas—those built on fill—may experience liquefaction, when saturated soils essentially behave like liquids. A recent study commissioned by ABAG projects between 2 and 9 inches of potential settlement at the Oakland Airport in a very large Hayward–Rodgers Creek earthquake.
Whether buildings collapse or homes slide off their foundations, it’s highly likely that connections to utilities—electricity, water, gas—will also break, raising the specter of fire.
Charles Scawthorn, a visiting research engineer at the Pacific Earthquake Engineering Research Center at Berkeley, has studied the risks of such fires, as well as the availability of water in the region after a quake to fight them. “If it’s pouring rain or a cold day and it happens at three in the morning when there’s less human activity, you’re going to have fewer fires and they’re going to spread slower,” he says. “If it happens during a workday and it’s a hot, dry, windy day, my god, it could be terrible.”
In a multifire scenario, many aggravating factors are at work that could confound firefighting efforts. For starters, as many as 1,700 roads may be closed throughout the region, nearly two-thirds of which are expected to be in Alameda County. In the earliest stages, this could well keep rescue workers from reaching trouble spots.
Even without blocked roads, fire personnel could simply be too busy at, say, the site of a collapsed building to respond to lesser emergencies. And with multiples scenes of disaster spread around the Bay, mutual aid between departments may be impossible. Meanwhile, water to fight fires may be scarce due to broken water lines.
Under such circumstances, the fires could quickly grow out of control, especially in high-density neighborhoods where wood construction predominates—a description that applies to wide swaths of the Bay Area.
The true impact of a major quake would not be limited to the immediate aftermath, however. Even weeks or months following the catastrophe, it could mean disrupted commutes, delayed supplies for recovery, interruptions in the flow of goods through the Port of Oakland as well as traffic in and out of the region’s airports.
A couple of years ago, U.S. Geological Survey scientist David Schwartz and his colleagues reexamined the Hayward Fault and concluded that the surface rupture of a quake, the actual shift observed in the ground, may initially be less than expected. The displacement might be small enough to be measured in inches—not the more striking, immediate six-foot displacement that some experts expect. But in the weeks and months afterward, there might be another four or five or six feet of additional catch-up movement, something geologists call “afterslip.”
Obviously, that poses substantial complications for engineers, who tend to plan for a single destructive event, not a continuing series of events. With afterslip, Schwartz says, “You repair something and it cracks again.”
We may also face a kind of social and economic afterslip that could persist for years. Mary Comerio, professor emeritus of architecture, and others worry about these long-term social effects, if-then scenarios that will play out across years. For example, if homes are damaged and temporary housing is in short supply, if aid is hard to come by, if businesses relocate and never return, if container ships skip the Port of Oakland due to infrastructure problems, then the Bay Area would experience lasting economic pain and social upheaval.
In a 2013 study by Risk Management Solutions of the potential consequences of a half-dozen different shaking scenarios, the company tried to put a dollar value on the economic and insured losses for residential and commercial property in the Bay Area. Factoring in risks from fire, as well as some of the longer-term effects on the economy, like labor shortages and litigation, the company concluded that a magnitude 7 earthquake on the Hayward Fault could mean as much as $190 billion in losses for the region.
For comparison, the cost of Hurricane Katrina was estimated to be $120 billion. As with that disaster, a Bay Area quake would no doubt bring displacement. Mary Comerio observes that roughly only 10 percent of California homeowners carry any form of earthquake insurance. “Where,” she asks, “is the money going to come from to repair all the damage?”
As Janiele Maffei puts it, “If you lose the population, you lose the engine behind the recovery.” Lower-income and minority groups will doubtless have the hardest time coping and entire neighborhoods may be vacated, as happened in Northridge’s seismic ghost towns and in sections of New Orleans. Physically and socially, the Bay Area that survives the quake will not be the same as the one that preceded it.
Says geologist David Schwartz, “We’ve never had a major earthquake in a modern U.S. metropolitan area, and we don’t know what the results really will be.”
Tim Lesle, M.J. ’08, is a regular contributor to California. You can tweet earthquake scenarios to him at twitter.com/telesle.
From the Summer 2014 Apocalypse issue of California.