Geoscientists and engineers help Haiti prepare for the next big earthquake
July 26, 2010
Within weeks of the Haiti earthquake last January, five geoscientists and two engineers from The University of Texas at Austin traveled to the island nation to help assess the damage, identify future earthquake hazards, and make recommendations about how and where to rebuild. They surveyed Haiti from the air, land, coastline and sea.
With the rainy season beginning in late April and hurricane season in July, they knew they had to act fast. Storm waves can quickly erase features on the near-coast seafloor related to the quake. Features associated with a number of small tsunamis that were triggered by the quake were also at risk of disappearing. For the engineers, it was just as important to assess the integrity of still-standing buildings before people reoccupied them and to make recommendations before the Haitians attempted to rebuild.
When Paul Mann first arrived in Haiti in late January, things were still in a state of "profound chaos." The country was reeling from one of the five deadliest earthquakes in recorded human history. Services for visitors such as hotel rooms, commercial air flights, rental cars, electricity and clean drinking water were largely nonexistent. Gunshots punctuated the blacked out nights of the devastated capital as looters ignored the curfew and picked through the rubble of destroyed businesses and homes.
Flying along with a camera crew producing material for the TV program "Nova," Mann and his colleague Richard Koehler from Alaska's Division of Geological & Geophysical Surveys were able to survey large areas of the island nation efficiently. With a bird's eye view of more than the geology, they saw homes built on alluvium (loose sediment washed down from deforested areas) that were now piles of rubble. They also saw smaller, hastily built post-quake homes that looked just as unstable as their precursors.
At one point, Mann and Koehler decided to get on the ground for a closer look at the geology. As they approached a flat field for a landing, they noticed throngs of Haitians streaming down mountain trails, some carrying metal bowls, eventually surrounding the helicopter.
"They thought we were with a relief agency," he said. "We didn't speak Creole. It was very awkward."
The magnitude 7 Haiti earthquake killed nearly a quarter of a million people and left more than one million homeless, mostly in the capital city of Port-au-Prince. Just over 20 years earlier, the just-as-powerful Loma Prieta earthquake jolted the San Francisco Bay area, killing 63 people and leaving several thousand homeless. Why such a stark difference?
It's now clear that a combination of shoddy building practices and environmental degradation set the stage for the disaster in Haiti. Decades of deforestation and the resulting soil erosion meant much of the soil people built upon in the capital city was unstable sediment. Add to the mix overcrowding, corruption and extreme poverty — Haiti is the poorest country in the Western Hemisphere — and the earthquake became a perfect storm.
As part of a National Science Foundation funded rapid response mission, Mann and his colleagues found evidence that the soils were shaken so violently they behaved like a liquid flowing across the landscape, a phenomenon known as lateral spreading and liquefaction. Earthquakes most likely caused by the same fault and resulting in the same soil motion destroyed Kingston, the capital of nearby Jamaica, in 1692 and again in 1907.
Red Light, Green Light
Wassim Ghannoum landed at the airport in Port-au-Prince just nine days after the quake as part of a team assessing the safety of still-standing buildings. About 80 percent of Haitian government buildings had collapsed, including the presidential palace. Vast numbers of government workers died. The president was running the country from a tent at the end of the runway at the capital's airport. The United Nations (UN), which had helped run the impoverished nation before the quake, lost 200 people when one of its main buildings collapsed. Police stations, hospitals and schools collapsed too. More than a million survivors were homeless, living in makeshift tents made of bed sheets.
Asked if he had ever seen destruction on this scale, he said it reminded him of Beirut after the Lebanese civil war.
"I just focused on my job, did what I had to do — get in, get out," said Ghannoum, assistant professor in the university's Cockrell School of Engineering.
The 10-person team, organized by the Multidisciplinary Center for Earthquake Engineering Research (MCEER) at the State University of New York Buffalo at the request of the UN, broke up into smaller units and spent a week visually inspecting 120 buildings. They focused on critical infrastructure such as hospitals, warehouses, orphanages, UN buildings and government buildings. Buildings that were safe to continue using they marked green. Those that were partially safe, but needed work, they marked yellow. Unsafe ones were marked red. Ghannoum said in some areas of the capital, a third of the buildings were pancaked and another third were "hanging precariously." Of the remaining third that were salvageable, most needed repairs.
The team made an important first step, but it would take follow-on crews several more months to complete the inspections.
In February, Sean Gulick co-led a sea-based expedition examining the underwater effects of the quake along with Marcy Davis and Matt Hornbach from the Institute for Geophysics, and colleagues from Lamont-Doherty Earth Observatory and the University of Missouri.
For two weeks, the team onboard the 185-foot RV Endeavor used sonar to map shifted sediments on the seafloor and seismic sensors to examine faults beneath. Funding was provided by the National Science Foundation and the Jackson School of Geosciences.
Earth's surface is made up of scores of plates or chunks of crust that shift and grind past each other. In some places, where two or more plates collide, the rock compresses and stress builds up. At some point, the rocks snap and an earthquake is triggered. That's exactly what the scientists suspected happened along part of the Enriquillo Plantain Garden Fault (EPGF) on Jan. 12.
The Endeavor team mapped the EPGF as it went offshore near the capital of Haiti, discovering a portion that broke in the earthquake as well as portions that didn't. When one part of a fault breaks, it transfers more stress to surrounding parts. Gulick, a research scientist at the Institute for Geophysics, noted that there are three nearby segments of fault that could be primed for another quake.
"There are at least three different ways this earthquake could trigger a subsequent quake: an earthquake farther west along Enriquillo-Plantain Garden Fault, an earthquake on the same fault to the east, again affecting Port-au-Prince, or even triggering an event on a neighboring fault," he said.
Fred Taylor, senior research scientist at the Institute for Geophysics, and Paul Mann (back in Haiti for a second trip) measured how much corals along the coast had risen or fallen to infer how the land shifted during the quake.
The scientists now think the geology beneath Haiti is far more complex than previously thought. In a paper submitted for publication to the journal Nature Geosciences, Taylor, Mann and their colleagues combined data from their rapid response expeditions, seismological observations, and measurements from space to show that the earthquake wasn't caused entirely, or even largely, by the EPGF. Rather, most of the motion was on previously unknown shallow faults, with only minor slip along or near the EPGF. The report ominously notes that much more strain is waiting to be released on the EPGF, possibly as another large earthquake.
Ellen Rathje, a professor in the Cockrell School of Engineering, was part of yet another land-based rapid response team sponsored by the National Science Foundation and organized by the Geo-Engineering Extreme Events Reconnaissance Association (GEER), an organization that documents how soils respond to earthquakes, hurricanes and other extreme events.
"We look at soil as an engineering material," she said, "and are interested in how soil conditions influence damage patterns across an affected area. Soil can increase damage levels by enhancing the levels of shaking or by failing catastrophically through soil liquefaction."
The information they collect helps inform seismic design practices and site location. She acknowledged that the earthquake hazard in Haiti can never be reduced to zero deaths.
"There are so many things that we can do that are relatively easy to implement that could have changed this earthquake from a 200,000 death earthquake to a 2,000 death earthquake," she said. "The technical community in the U.S. is asking whether we should be spending all of our time working hard so that the next big one in San Francisco kills 50 people instead of 80, or whether we should focus our efforts so we help these communities dramatically lower their vulnerability?"
She said from an engineering standpoint the solutions are straightforward, but Haitians will have a hard time rebuilding safely because of poverty, corruption, poor understanding of the science of earthquakes and a lack of engineering standards.
When the earthquake struck, there was a cloud of white dust from all of the collapsing concrete, the primary building material in Haiti. It was common for people to use dirty sand dug out of creeks, mixed with too much water and too little concrete mix.
"This stuff crumbles in your hand," said Mann. "And what they call rebar isn't what we think of as rebar in the U.S. It flexes too easily. It's smooth so it doesn't bond to the concrete."
Rebar, or reinforcing bar, is a steel rod embedded in concrete to give it added strength. The three scientists who spent significant time on land — Rathje, Ghannoum and Mann — all recounted seeing Haitians digging through the rubble of collapsed buildings to pull rebar from the crumbling concrete. Rathje said she's worried they'll just straighten it out and reuse it in new buildings with the same poorly mixed concrete.
"Have you ever fiddled with a paper clip where you bend it back and forth?" asked Ghannoum. "It snaps. It no longer has its strength. On the one hand, you understand they're so poor. On the other hand, if they don't do anything better, they're just repeating the same mistakes."
The scientists from The University of Texas at Austin all said it is critical that Haitians develop local expertise in earthquake science and in constructing buildings to withstand quakes. A Haitian government scientist and two local university students participated in the Endeavor cruise, learning the latest concepts and technologies in earthquake science.
Haitian scientists also accompanied Rathje on her second trip to Haiti. Rathje, who serves on the board of the Earthquake Engineering Research Institute, said their organization is trying to establish a regional chapter in Haiti.
"The idea is to do short courses and training seminars and set up a library so that they have the technical materials and really try to build the education in the country with respect to earthquake and seismic design," she said. "We can't just come in for a week and then leave and expect that to change anything."
Ghannoum is working with two other engineering professors from his rapid response mission to develop an exchange program in which they will go to Haiti for a few weeks each year to teach university classes in structural assessment and seismic design, as well as workshops for the public. Students from Haiti could also come to the U.S. for more extensive training.
The engineers said it really doesn't matter when or how the next big earthquake might happen. What matters is that now people realize large earthquakes can happen in Haiti. Haitians rebuilding their homes and businesses, and the aid agencies helping them, should take that threat seriously, they said.
For more information, contact: By Marc Airhart
Geology Foundation, Jackson School of Geosciences