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Need to know

Have Strict Seismic Codes Saved Chile?


Clayton DeKorne

Strong seismic building codes are getting credit for keeping the death toll low - only six deaths as of Wednesday morning - after Chile was hit with an 8.2-magnitude earthquake on Tuesday (see "Experts: Strict building codes saved lives in powerful Chile earthquake," CNN, 4/3/14).

In reference to Chile, John Bellini, a Denver-based geophysicist at the U.S. Geological Survey told CNN: ""They're a seismically active region of the world and they are very good at implementing their building codes similar to California."

California's current seismic codes, which, along with Japan's, serve as a model for country's throughout the world, were developed largely in response to the Loma Prieta quake the leveled neighborhoods in teh Bay Area in 1989. (See JLC's coverage of this event and a description of the basic bolting and bracing procedures required to keep wood-framed buildings on their foundations in Seismic Bracing, JLC 3/90). Details on retrofit strategies are further explained in "Seismic Support for Old Foundations," JLC 4/97)

Bellini points to a 2011 report by the United Nations Office for Disaster Risk Reduction that compared an earlier 8.8-magnitude Chilean earthquake in 2010 (see "Chile Earthquake Pictures: The Aftermath," National Geographic, 4/1/2010) to a much more devastating earthquake that same year in Haiti. The reported credited Chile's "strict building codes" for playing "a large part in protecting people."

"That's actually a perfect example of the differences in building codes and enforcement in two different regions," Bellini is quoted saying by CNN. "Any place that has a magnitude 7 or an 8 is going to have some kind of damage. However, the building codes play a large part in the damage and destruction that is seen, as well as the casualty level. Population density plays an important part as well -- but the building codes are really what can save lives in areas that have large earthquakes."

The 8.2-magnitude earthquake in Chile was 89 times stronger than 6.9-magnitude Loma Prieta quake that leveled neighborhoods in the Bay Area in 1989, and 44668 times stronger than the 5.1-magnitude La Habra quake that rocked L.A. last week. (Earthquakes are now measured on the "moment magnitude scale," a much more accurate measure of the "energy released" by an earthquake than the Richter scale's measure of earthquake "size." See the U.S.Geological Society "How Much Bigger ... Calculator" and "Moment Magnitude Explained—What Happened to the Richter Scale.")

Chile may not be out of the hot seat yet, however. Tuesday's quake was one of 300 smaller quakes that have shaken northern Chile in recent weeks, and there is strong speculation that the surge in the region's seismic activity may just be the opening act to an even larger event .

The USGS estimates that several million earthquakes occur in the world each year. Many go undetected because they hit remote areas or have very small magnitudes. The NEIC now locates about 50 earthquakes each day, or about 20,000 a year.


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