Almanac

News - February 24, 2010

Haiti quake has lesson or two for Bay Area

by Dave Boyce

The Peninsula, and Portola Valley in particular, has something in common with Haiti: adjoining tectonic plates that move horizontally relative to each other, and in different directions. As pressure builds, they can slip abruptly in a so-called strike-slip earthquake, which is what happened in Haiti in January at a cost of more than 200,000 lives.

Earthquakes both here and there have been and will continue to be violent, but the aftermaths do not have to be catastrophic, as U.S. Geologic Survey geophysicist Bill Ellsworth reminded the Menlo Park Rotary Club in a presentation on Feb. 17.

In his talk, "The 2010 Haiti earthquake: A tragedy that did not have to happen," Mr. Ellsworth explained why buildings tumbled in and around the capital city of Port-au-Prince after the magnitude 7.0 quake.

The damage from the magnitude 6.9 quake that hit the Bay Area in 1989, including the collapse of the Cypress Freeway and ground liquefaction in San Francisco's Marina District, was limited compared with what happened in Haiti, but similar on a smaller scale and in the underlying geology.

What happened in Haiti, and why? Are there lessons in it for us?

The Almanac talked with Mr. Ellsworth; with his USGS colleague Walter Mooney, a geophysicist who had just returned from nine days in Haiti; and with earth scientist Brian Tucker, president of the Palo Alto-based nonprofit Geohazards International, whose worldwide mission since 1991 is to educate vulnerable communities on how to survive large earthquakes.

Hurricanes a priority

Hurricanes regularly visit Haiti, while the last big quake was in 1770, Mr. Mooney noted. The buildings there, with heavy concrete floors and roofs, were built to withstand a hurricane's high winds. The columns holding up the floors were not built to withstand ground waves.

"They hadn't thought too much about earthquakes because it's been 240 years," he said. Those buildings represented a "very high vulnerability" that led to "dramatic pancaking" — the collapse of upper floors, one on top of another.

Mr. Mooney said he talked with many Haitians who "have absolutely no intention of going back to heavy concrete construction."

A broader concern, he added, is large cities such as Lima, Teheran, and New Delhi — and the American Midwest — that have vulnerable structures on or near faults that break on intervals of hundreds of years. Builders may take chances on non-compliant structures that have lifetimes of 30 years or so.

"It's a bad bet," Mr. Mooney said. "The fact that (quakes) are infrequent doesn't mean that they're inconsequential."

Local concerns

In the Bay Area, Mr. Ellsworth said, among vulnerable buildings are those built before 1980 and not retrofitted to address so-called "soft" first floors — ground floors used for parking or retail and not fitted with shear walls to prevent sideways movement.

Retrofits tend to cost a fraction of the building's total value, he noted.

Also vulnerable are un-reinforced masonry and non-ductile concrete frame buildings, structures whose framing is neither wood nor steel, he said. They are harder to spot. "It takes earthquake engineers with their X-ray vision," he said.

A 1980s-era program to strengthen un-reinforced masonry buildings in Los Angeles paid a huge dividend when most of them withstood total collapse in the 1994 Northridge quake, he said. "We know these engineering solutions work," he added.

Science lessons

Plate tectonics theory is not well understood in the developing world, where earthquakes tend to be thought of as acts of God, Mr. Tucker of Geohazards International said.

"If people would believe that earthquakes are recurring and will recur," he said, "then we could make some progress. That is, particularly in Haiti, not the case."

The developed world may sniff at such ignorance, but there can be a price. The deaths in Haiti included 5,000 U.S. citizens, Mr. Tucker noted. "Helping developing countries prepare for earthquakes and reducing their capital losses is in our own selfish best interests," he said. "It's not just humanitarian."

The problem is explaining a danger that is real but not predictable, Mr. Tucker said. In his experience, people begin to respond favorably when they understand the threat to schools.

In sessions held worldwide, Mr. Tucker said, he has asked questions to gauge when people will agree to publicly funded safe buildings. Concern starts with approximately zero for parliaments, then works its way up through religious institutions, workplaces and residences.

"The real clincher is schools," he said, because the government owns them and no one misunderstands the duty to make them safe.

Sometimes that isn't enough. Many schools collapsed in the 2008 Sichuan quake in China. Did Mr. Tucker take his message there?

He considered it, he said, but noted that a man there who questioned the official explanation as to why the schools collapsed recently received a five-year prison sentence on subversion charges.

"We are exposing problems and motivating grass-roots action to address those problems," he said. "The kind of work we do just doesn't work in China."

Geohazards' Web site is www.geohaz.org.

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