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What's also concerning is that more than fifty Bay Area health clinics are on the list of buildings likely to collapse or be irreparably damaged in a large earthquake, according to California Human and Health Services' data from May of this year.
Using a scale of one to five, with five indicating structural soundness, the agency assessed hundreds of hospitals and clinics statewide for seismic structural integrity. Of 147 in the East Bay, 27 received a rating of one, which means that the facility poses a "significant risk of collapse and danger to the public," according to the state. Twenty-five more buildings were rated two.
Even soundly built homes and other structures may crumble in the Big One due to a phenomenon called liquefaction, by which soft, unstable soil actually turns and roils in an earthquake — much the way coffee and cream can blend in a roughly vibrated mug. Liquefaction, a familiar term to anyone studying earthquakes in the Bay Area, is a potentially devastating process that has, in places, destroyed entire neighborhoods and cities. Liquefaction can knock large buildings off their foundations and tear apart pipelines, especially in places built on artificial landfill. The damage in Kobe, Japan, was largely attributable to liquefaction of sand and gravel soil.
Much of the developed area along the Bay's shoreline — such as the Port of Oakland, for one — sits on artificial fill.
"And we saw how well artificial fill held out in Loma Prieta," Zoback said, referring to San Francisco's Marina District, where liquefaction practically overturned entire homes and duplexes.
To help protect against liquefaction, local water suppliers are replacing pipe networks with thicker, stronger tubing. But work crews are progressing at only about thirty miles per year. This means there is little chance of completing the upgrades before the next large earthquake, and there will surely be countless ruptures when the Hayward or San Andreas faults slip again. Plumes of leaking gas will almost certainly burst into flames, and this could be the source of most of the damage.
Even Berkeley professor Sitar, who says most risk-assessment models exaggerate predicted damage and death tolls from earthquakes, thinks fire will deal the greatest blow to the Bay Area when the Big One hits.
"That is how we might see a large loss of life," he said.
Are We Prepared?
If you stroll along Dwight Way in Berkeley, the hustle of downtown disappears a block at a time. Near the top of the long grade, the street eventually dead-ends at a public park. But never mind the idyllic Berkeley Hills scenery; be sure to take notice of the cement sidewalk. Just past the intersection with Hillside Avenue, the curb abruptly turns in several inches, offset by the slow — slow — migration of the Earth's surface on either side of the Hayward Fault. This is rare, and marvelous, visual proof of plate tectonics in action.
The south wall of the UC Berkeley campus stadium, too, shows unmistakable evidence of what scientists call "fault creep." So do numerous other curbs, rock walls, and sidewalks along the fault, which scientists say is creeping several millimeters every year.
But the most famous visual indicator of local fault creep, the spectacularly offset curb at Rose and Prospect streets in Hayward, was eliminated earlier this summer by a maintenance crew, who replaced the sidewalk with a wheelchair ramp, much to the sorrow of geologists and earthquake buffs.
The point here is that every pipe, roadway, train line, and other solid structure that crosses the Hayward Fault and is not modified with state-of-the-art protections will be broken, cracked, ruptured, or entirely sheared in half when the fault line suddenly slips several feet at once. Hudnut at the USGS reminded that there are several hundred buildings that sit smack on the Hayward Fault.
Fortunately, local agencies have gotten a jump start on protecting this infrastructure against rupturing. For example, the two large pipelines that deliver water to San Francisco cross the fault in the East Bay hills, and the S.F. Public Utilities Commission has seismically retrofitted them. The pipes are six-and-a-half feet by eight-feet wide, and are now encased in concrete vaults hundreds-of-feet long, where they cross the Hayward Fault in Fremont, just underneath Interstate 680.
The vaults are sectioned so they can accommodate horizontal displacement along the fault of as much as six feet without the rigid pipes breaking. The pipes themselves are fitted with ball and slip joints within the concrete vault to allow them to rotate and shift. The project cost $75 million and took three years to complete, wrapping up in late 2015.
Similar engineering was used about a decade ago to protect the major pipeline that delivers water to 800,000 people on the west side of the East Bay hills, according to Andrea Pook, a spokesperson with East Bay Municipal Utilities District. EBMUD's main transmission pipe leads from the Delta and through the hills via the nine-foot-wide Claremont Tunnel. Inside the tunnel, where the pipe crosses the Hayward Fault, it rests on rollers so that, when the fault slips, only the tunnel walls will rupture, allowing the pipe to shift unharmed.