Understanding Why Haiti's Buildings Collapsed

Haiti's presidential palace, with its spaciousness and sparkling white façade, was a jewel in the heart of a city that has withstood civil wars, military coups, and decades' worth of hurricanes. In the hours after last Tuesday's earthquake, its collapse was cited as a proof of the severity of the crisis at hand. In the days since, it has come to symbolize something more: a government on the verge of a complete meltdown in a country too poor to build even its most central structures properly.

In scientific terms, the palace's fate can be explained by far simpler principles: too few columns, too many open spaces. It's what engineers call the "soft-story effect": when an earthquake hits, a building that has sacrificed structural support for the sake of artistry is bound to collapse. But while the felling of some buildings is easy to explain, other questions linger—namely, how stable are the structures that remain, what role did soil quality play in the devastation, and what might a future, earthquake-resistant Port-au-Prince look like?

Structural engineers hope to answer those questions and more in the coming weeks as they deploy to Haiti with the next wave of relief workers. "From an engineering standpoint, an earthquake's aftermath is like a living laboratory," says Brady Cox, an engineering professor at the University of Arkansas. "It provides valuable, site-specific information that can guide reconstruction efforts and inform building codes." But scientists must act quickly, before weather events and general chaos muddy up the crime scene. As a member of the National Science Foundation–funded GEER (Geoengineering Extreme Events Reconnaissance), Cox has deployed to Japan, Peru, Turkey, and elsewhere to study structural failures in the immediate aftermath of severe quakes. He and other GEER members will deploy to Haiti next week.

One of the first things Cox plans to do is test the soil surrounding some of the most decimated spots and compare it with the soil around buildings that have managed to withstand the quake and its aftershocks. Earthquake shaking tends to increase water pressure in the ground, which in turn makes the soil weaker. As water molecules force themselves in between grains of sand, the ground loses its ability to support a building or maintain a slope. Some soils are far more susceptible to this process (known as liquefaction) than others.

Knowing where the most vulnerable soils are will help scientists develop a set of recommendations about just where some neighborhoods should be rebuilt. "Right now, it looks like there is massive, so far uncoordinated, resettlement activity," says Marc Levy, deputy director of Columbia University's Center for International Earth Science Information Network. "We're concerned that people may be moving from bad spots to worse ones." In Taiwan in 1990, for example, a devastating series of typhoons forced thousands to relocate to patches of hillside that proved particularly vulnerable to landslides. Levy's team is working to assemble information about multiple hazards—from landslides to earthquakes to floods—onto a single map that will ultimately be used to guide reconstruction.

In addition to more pillars in the palace, a stronger Haitian capital will have to include more earthquake-resistant housing. And while such engineering is expensive, there are some cost-effective options that experts say could be a good fit for Haiti. Straw-bale houses, which are already being built in Pakistan, have proved to be just as resistant as other earthquake-proof designs, at only half the cost. In one recent study, the houses—made of clay, soil, straw, and gravel, and built by unskilled laborers—withstood forces comparable to the 6.7-magnitude earthquake in Northridge, Calif., in 1994.

Of course, there are other, more obvious steps toward building a stronger, more resilient Haiti. The concrete used in most of the buildings, for example, was dangerously light on cement. (Concrete is essentially small rocks and gravel stuck together with cement. The cement is the expensive component, but it's also the most essential part as far as durability is concerned. Cheap concrete has less cement and produces weaker buildings.) On top of that, pictures indicate that most of the buildings in Port-au-Prince lacked proper reinforcements. "In many of the smaller buildings, you just have cinder blocks piled on top of one another with no supports of any kind," says Cox. Concrete by itself can handle compression stresses, but reinforcements made of steel, rebar, or even rope are needed to resist tension stresses.

A large part of these deficiencies is no doubt the result of dire poverty, but experts say another problem is the rampant corruption in Haiti's construction industry. "They simply don't enforce any building codes," says Pedro de Alba, a civil engineer and earthquake engineering expert at the University of New Hampshire. "That alone can mean the difference between losing 100 people and losing 100,000 people." Case in point: in 1989 a 7.0 earthquake in San Francisco killed fewer than 70 people, largely thanks to stable buildings that had been designed with earthquake resistance in mind. "It's a good rule of thumb that earthquakes don't kill people, collapsed buildings kill people," says de Alba. "And we have the ability to drastically minimize structural collapse, even in regions this poor, even with earthquakes this severe."

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