Rising from the rubble — 30 years after Loma Prieta
Santa Cruz is a model of resiliency and preparedness for future quake disasters
SANTA CRUZ >>
This week’s burst of earthquakes ended this city’s stretch of seismic calm, reminding residents of the magnitude 6.9 Loma Prieta temblor that almost destroyed it 30 years ago Thursday.
But downtown’s newest building never flinched.
Built in the hole that once held a beloved 1890s-era brick bookstore, the ambitious $35 million Park Pacific project is secured by a sunken array of stable columns, a 2-foot-deep concrete mattress, more flexible framing and other stateof-the-art engineering practices.
Reborn as a symbol of resiliency, this sunny coastal city is braced and bolted — a model of earthquake preparedness in a place that knows there will be future disasters.
“We are doing the best we can,” said city historian Ross Gibson, who grieves the loss of downtown’s countercultural charm yet welcomes the new structural engineering that will help save lives. “It is all a learning experience.”
All over the Bay Area, government agencies and private and nonprofit sectors have invested $73 billion to $80 billion in 700 structural retrofits and replacements to create a metropolitan area that could better withstand a Loma Prieta-size earthquake, according to the U.S. Geological Survey. On Oct. 17, 1989, that 6.9 temblor killed 63 people, injured more than 3,700, destroyed 366 businesses and 11,000 homes and caused $6 billion in property damage.
Hospitals are sturdier. Elevated freeways and bridges offer better support. Major water pipes now bend, not break. Natural gas pipelines have earthquake-resistant electrical equipment, springlike metal transmission lines and automatic shut-off gas valves in fault areas.
To be sure, some projects still await completion. BART will finish its new “slinky” version of the 6-mile-long Transbay Tube retrofit by fall 2022.
On the main suspension span of the Golden Gate Bridge, a retrofit is being designed, with construction to be completed by 2026.
Moreover, local roads, utility distribution lines and many homes have yet to see upgrades. And there are deep concerns about telecommunications. AT&T and Verizon, two of the Bay Area’s largest cellphone providers, say their systems seismically are up to date but haven’t revealed how these lifelines would be affected in a worst-case quake
scenario.
Meanwhile, the region’s population has surged from 6 million in 1989 to 7 million, with one of the world’s highest concentrations of wealth and innovation.
And the next earthquake to challenge our cities may not rupture in the remote Santa Cruz Mountains, like the 1989 temblor.
It may be underneath our feet.
Monday night’s magnitude 4.5 earthquake that jolted Concord and Pleasant Hill in the East Bay could be felt from Vallejo to San Francisco. It was centered on an unnamed fault between two larger faults, the Hayward and Calaveras. Tuesday afternoon’s magnitude 4.7 earthquake, rattling San Jose and the South Bay, erupted near Hollister along the San Andreas fault.
But each new major earthquake inspires innovations in structural engineering.
“As we study each earthquake and prepare, we change how we retrofit and build new construction,” said Jeff Brinks, vice president of DCI Structural Engineers, which works with Swenson Builders around the Bay Area.
San Francisco’s slender One Rincon Hill South Tower — 60 stories tall — has a technology called “tuned liquid sloshing dampers,” which reduce the vibration that can lead to structural failure, as well as reinforced concrete shear wall at its core and special bracing, said USGS earthquake engineer Mehmet Celebi.
Dampers also were installed in the 13-story Santa Clara County Government Center in downtown San Jose.
During the Loma Prieta earthquake, “That building had a serious problem,” Celebi said. “It was vibrating like a crazy dog.”
Kaiser Redwood City’s new hospital is equipped with “buckling restrained braces,” designed with a slender steel core, a concrete casing and a layer of material that decouples the two — absorbing the energy from an earthquake, he said.
In addition to bracing and shear walls, Oakland’s historic City Hall, which was uninhabitable after the quake, was retrofitted with a state-of-theart seismic base isolation system, hidden in its basement. The building sits on several huge shock absorber bearings built between the building and the ground, allowing the structure to slide back and forth but remain upright.
The new Apple building uses the same technology,
mounted on 700 base isolators that let the building — with 6 miles of precious glass — move as much as 54 inches in any direction during a quake, said structural engineer Jawed Umerani of Palo Alto’s Umerani Associates Inc., part of the design team behind the Apple campus.
“The building can slide and not hit anything,” said Umerani.
At the new Stanford Hospital, an estimated 10,000 braces hold utility pipes and ductwork, according to Bert Hurlbut, vice president of new hospital construction at Stanford Health Care. The hospital’s atrium — made of about 11,000 square feet of glass panels — relies on caulking to deform during an earthquake, with a film of plastic to protect against falling shards.
While new construction is designed to flex and bend, older retrofits must stiffen, strengthen and often preserve historic elements, said Ron Coté, senior vice president of Swenson Builders, which retrofitted the dangerous unreinforced masonry
of San Jose’s St. James Hotel, Hayes Mansion, Security Building, Letitia Building, Knox-Goodrich Building and others.
The challenge faced by Santa Cruz was how to protect both its past and its future. It lost a total of 31 buildings. And many of its surviving structures needed better protection.
At stake was its survival — and its soul.
The iconic Pacific Garden Mall, a leafy street that snaked through the heart of downtown, was ruined. A bit threadbare, with little nightlife and a quiet retail and restaurant scene, this was the heart of blissful counterculture. In the sleepy evenings, “Rainbow Ginger” Johnson played the tambourine and twirled in front of the old Cooper House, as soft music played.
“It was beautiful. It represented a whole culture in an era of peace and love, with an ethos that you should be friends with everybody,” recalled Gibson. “And once that had been uprooted, very literally, it left behind holes in our heart.”
Now there’s a different downtown. It’s commercial and bustling. Seedy bars and bong shops have been replaced by pricey retail shops, a museum, an organic ice cream store and restaurant crowds that spill into the street.
Only one dangerous unreinforced masonry building remains — and it’s vacant, said John McLucas, an official with the Santa Cruz Planning and Community Development Department. The rest of the old “soft story” storefronts now have large footings with resilient frames, better bolting, braced roof parapets and injected epoxy into the grout joints of the brick walls.
The new Park Pacific project — a five-story, 6,000-square-foot project fronting Pacific Avenue and Cedar Street — is emblematic of the change. The site of the quaint Bookshop Santa Cruz and Santa Cruz Coffee Roasting Company will house a restaurant, parking garage and 79 modern condominiums, engineered to meet tough new standards.
“The earthquake was a chance to look farther ahead into the future,” said Tom Brezsny, a 40-year resident of Santa Cruz and realtor with Sereno Group Real Estate. “It was a blank slate. All bets were off.”
“Santa Cruz had no choice,” he said, “but to reinvent itself.”