OREGON STATE UNIVERSITY

Tale of two earthquakes offers lesson for other major cities

03/08/2010

CORVALLIS, Ore. – The two earthquakes that recently struck Haiti and Chile both caused devastating destruction, but also offer an important contrast in loss of life – and a clear warning to other cities around the world that share problems of poor construction, weak building code enforcement, lack of emergency services and nearby faults capable of large earthquakes.

The Haiti disaster was caused by a large earthquake of magnitude 7.0, but killed more than 200,000 people. The magnitude 8.8 Chilean earthquake on an offshore subduction zone was vastly more powerful, but so far the loss of life has been estimated at about 500 people. Buildings were badly damaged but they held together well enough to greatly reduce the number of deaths.

According to earthquake and engineering experts at Oregon State University, the far greater death toll in Port-au-Prince, Haiti, is primarily a reflection of substandard construction, and reflects a situation that many other heavily populated cities must come to terms with if they are to avoid a similar catastrophe.

“There is a tremendous difference in the effects of an earthquake in a developed country and in the developing world,” said Robert Yeats, a professor emeritus of geosciences at Oregon State University, earthquake expert and author of an upcoming book, “Active Faults of the World.”

“Earthquakes like Northridge, Calif., in 1994, Kobe, Japan, in 1995, and even the recent huge earthquake in Chile did take a significant number of lives, but much of the damage was confined to buildings and infrastructure,” Yeats said. “There are other cities around the world where similar earthquakes could kill a million people, and they will unless we better prepare for them.”

In work on his new book about six months ago, Yeats forecast one city in particular that faced risks from the Enriquillo-Plantain Garden Fault in the Caribbean Sea. “The poor state of construction. . . indicates that when the next large earthquake strikes, it will be a catastrophe,” Yeats wrote. The city he referred to was Port-au-Prince, Haiti.

According to Scott Ashford, professor and head of the School of Civil and Construction Engineering at OSU, the seismic risks many urban areas face can be quantified, as they relate to such issues as fault rupture, ground shaking, liquefaction, landslides and potential tsunamis. Construction practices can help deal with many of these concerns, and in combination with education and an effective social response network make an enormous difference in saving lives.

“Earthquake resistant design requires good materials but is mostly in the details, like hooking rebar to prevent columns from buckling or installing shear walls to prevent weak overstories,” Ashford said. “We know how to do this. But for it to work, cities have to adopt modern building codes and then enforce them, which means inspection without corruption. That’s what most of the problem was in Haiti.”

History has shown that many nations and cultures have resisted admitting the risks they face and doing something about them – failures not always confined to the developing world, Yeats said.

“Even after the great San Francisco earthquake of 1906, California government officials and city leaders actively covered up the real extent of the damage,” Yeats said. “They thought it would be bad for business, and blamed most of the problem on the resulting fires, not the earthquake. A propaganda machine in Los Angeles later did the same thing. It wasn’t until the 1933 Long Beach earthquake destroyed many school buildings and parents became outraged that the state really started taking its earthquake issues more seriously.”

But even as the science of earthquakes, fault behavior and construction techniques continues to improve, the OSU experts say, it’s apparent that many cities face enormous risks they are probably not prepared for. Not all situations are identical, and some are worse than others. But definite areas of concern include:

  • Kabul, Afghanistan – Even as the U.S. pours billions of dollars into this war-torn nation, little attention is paid to earthquake risks in this major city with millions of residents. It sits near the active Chaman fault and has millions of people living in ruins that would collapse during a major earthquake, potentially killing 100,000 or more.
  • Karachi, Pakistan – With a population of more than 15 million, this huge city has large areas of poorly constructed buildings, lies near a perilous “triple junction” where three tectonic plates meet, and yet the government continues to assess its earthquake risk as only “moderate.”
  • Yangon, Myanmar – This huge city, previously called Rangoon, lies close to the Sagaing plate boundary fault, as does a new capital being built further north.
  • Istanbul, Turkey – This city lies near the North Anatolian fault that produced two major earthquakes in 1999 east of the city, and another one in 1912 west of the city, and faces large earthquake risks because the fault lies just offshore to the south. Experts believe the probability of a major earthquake in the city is among the highest in the world. It has modern building codes but enforcement has often been lacking.
  • Managua, Nicaragua – This capital city was largely destroyed by a moderate 6.2 magnitude earthquake in 1972, with the damage largely the result of poorly constructed buildings.
  • Caracas, Venezuela – Several major cities in Venezuela are located on or near active faults, including Caracas, and building practices are poor. An earthquake in 1812 in Venezuela may have killed up to 10 percent of its population.
  • Kingston, Jamaica – This city, which has more than one-third of Jamaica’s population, is astride a tectonic plate boundary and has suffered repeated earthquakes, including one in 1692 that destroyed nearby Port Royal. The death toll from a major earthquake could be huge.

“In the developed world, we have to reach out to people in these nations, help them to better understand and accept the risks they face, and prepare for them,” Yeats said. “In the U.S. we’ve made progress, but even so have had our own problems facing up to earthquake hazards. Here in the Pacific Northwest we’re still not adequately prepared for the major earthquake we expect on the Cascadia Subduction Zone, which is quite similar to the fault that just ruptured in Chile.”

“Major earthquakes near large cities around the world are inevitable,” he said. “The loss of hundreds of thousands of lives is not.”