06 February 2004
Earthquake Research Groups Seek Lessons from Bam Earthquake
Construction codes seen as key to reducing death, damage
By Armond Caglar
Washington --- The Earthquake Engineering Research Institute (EERI), a California-based non-profit technical group, is partnering with the International Institute of Earthquake Engineering and Seismology in Teheran to draw lessons from the disastrous earthquake that struck the Iranian city of Bam in December.
"The information and lessons our EERI team will bring back from Iran can ultimately find their way into improved codes and practices and new research into improved, more cost effective retrofit techniques for existing structures, and the design and construction of new buildings, bridges, lifelines, emergency response and preparedness procedures," said Susan Tubbesing, EERI's executive director in Oakland, California.
Tubbesing said she expects that study of the Bam quake also will yield lessons on mass casualty care and interim shelter. "These lessons would not only benefit the United States, but countries throughout the world," she said. The EERI sent a team of engineering seismologists, geotechnical engineers, and environmental risk experts.
EERI President Thomas O'Rourke said the crucial factor in the differing levels of death and destruction caused by earthquakes is the implementation of building construction codes, not the intensity of the tremor.
To illustrate his point, O'Rourke said that on December 22 the California city of San Simeon was hit by an earthquake of the same magnitude as the 6.6 Richter scale quake that struck Bam on December 26.
Both quakes were located on top of seismically active regions and occurred at a depth of eight kilometers below the earth's surface. Despite their similarities, their human consequences were vastly different. The California quake left two people dead and 40 buildings damaged. The Bam earthquake is believed to have killed at least 35,000 people and flattened 90 percent of the buildings in the city.
"For both earthquakes, the main causes of damage and death were weak and vulnerable buildings," O'Rourke said. "In California, most damage was confined to the unreinforced masonry structures that were built of brick or mortar with no support or metallic strengthening. The buildings in Bam were adobe structures with little or no reinforcing or seismic detailing," he added.
Tubbesing said the United States has never experienced death and destruction from an earthquake of the scale of Bam, but said that a prospect for huge losses is a reality in the San Francisco Bay area of California, where an estimated six million people are at risk from the Hayward fault line. As a result, she said, communities in California have banned traditional adobe construction outright and are working to inform owners of concrete buildings with insufficient steel reinforcement of the vulnerabilities to earthquakes.
"We hope that some of the observations in Iran will stimulate these communities to adopt and enforce building codes that will prevent unsafe masonry construction and provide incentives for the retrofit of existing risky buildings," Tubbesing said.
An Iranian-American architect, Nader Khalili, has developed a "ceramic" or "super adobe" construction material as a substitute for traditional adobe. "Super adobe" methods are based on ancient clay building styles. They use a dome-shaped design and withstand severe heat, cold, rain, snow, wind and earthquakes. For more information on "super adobe," see the website: http://www.thesustainablevillage.com/servlet/display/product/detail/26658/.
Despite its vulnerability to earthquakes, California is still one of the safest states in the United States against earthquake damage thanks to codes for new building construction, experts say.
The structural engineering with respect to building codes includes methods, such as reinforcing a building's "cripple" walls with plywood to add lateral strength to an area of a structure generally believed to be the weakest point. "Cripple walls" are the area between the foundation and the first floor of a building and are prone to great stress during earthquakes from powerful lateral force.
Other techniques include bolting the frame of the house to its foundation, using special "anchor bolts," which ties the structure down securely, making it less brittle and prone to severe damage.
Additional methods include improving connections between floors and roof, and walls and roof, experts say. This can be accomplished with improved steel connections and also by inserting external steel frames, or "X-shaped" frames, in the structure.
Some communities in the United States, such as San Leandro, California, have offered on-line, ‘do-it-yourself' tips for people who wish to retrofit, or upgrade, their existing homes or businesses with simple seismic detailing.
Experts say that retrofitting existing structures -- for example, replacing masonry chimneys with light metal ones and using flexible gas line connectors to water heaters to prevent fires and explosions from gas line breaks -- can be the key between life and death during earthquakes.
The U.S. Geological Survey, an agency of the U.S. Interior Department, has played a large role since its inception in 1879 in earthquake research and the development of techniques to minimize earthquake damage.
In the United States, where an estimated 75 million Americans in 39 states are at risk from earthquakes, the USGS, through its Earthquake Hazards Program (EHP), aims to reduce the hazards caused by powerful temblors.
Using a three-fold approach, the EHP initiative includes comprehensive risk-assessment and identification of existing structures throughout the United States, extensive earthquake monitoring through its Advanced National Seismic System (ANSS), a complex web of installations currently being installed throughout the United States, and also school education programs, aimed to improve understanding of earthquake occurrences and their effects.
Ultimately, the USGS believes that this program will help to reduce injuries, deaths, and property damage caused by earthquakes. The ANSS, currently with 300 installations nationwide, can provide rapid information on earthquake intensity and ground shaking when earthquakes occur. Similarly, the information gathered on ground shaking can allow seismologists, engineers, and other experts to gather the scientific data they need to improve building designs for the future.
Paramount to the mission of the USGS earthquake program has been communicating the importance of building codes across the United States. The codes, often called "the public's first line of defense against earthquakes," are specifications mandated at the local level to identify the level of earthquake that buildings in that region must be constructed to withstand. The building codes have been proven to reduce deaths and property damage from earthquakes in the United States.
"Structures built to these standards are much safer in earthquakes than structures built 50 or even 25 years ago," the USGS says on its website. "In recent earthquakes, buildings built to modern codes have generally sustained relatively little damage."
(Distributed by the Bureau of International Information Programs, U.S. Department of State. Web site: http://usinfo.state.gov)