Riding the Waves
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The high frequency of damaging earthquakes throughout the past six months has raised many questions as to whether or not we have encountered a new trend in seismic activity – one that will continue to devastate heavily populated areas and their inhabitants. Individuals in the construction industry have begun to reevaluate their adherence to local, national and international building codes in an effort to prevent some of this damage. And metal is no exception, with steel-framed buildings having been extraordinarily successful at withstanding the seismic shock that can quickly reduce a less secure structure to rubble, or cause irreparable damages.
But it’s important to notice another set of trends among the chain of seismic outbursts that have plagued Southeast Asia, Latin America and most recently, Southwest portions of North America.
According to the U.S. Geological Survey, several million earthquakes occur worldwide each year. The installations of, and advances in technology of seismographs have yielded the detection of more earthquakes. The USGS, however, reported that the number of earthquakes of magnitude 6.0 or higher have remained relatively constant. An average of 134 earthquakes with magnitude 6 to 6.9 hit annually across the globe. The number lessens significantly as the intensity rises, with an average of 15 with magnitude 7 to 7.9 and only one with a magnitude 8.0 or greater each year. Chile’s earthquake this past February clocked in at an 8.8 magnitude, hopefully satisfying the “average” for this year.
But having experienced so many intense earthquakes in so short a time period, it’s easy to see the effects – and how these effects vary globally. A striking case for the need for adherence to seismic building codes and for the continual research into structural materials that can withstand seismic shock is the 6.8–magnitude quake and its 33 aftershocks that hit the Republic of Haiti this past January.
It’s no secret that the nation’s dilapidated infrastructure was partly to blame for the extensive damage incurred. About 80 percent of Haitians live below the poverty level in a nation regarded as being the poorest in the Western Hemisphere. The January earthquake, with its epicenter only 15 kilometers southwest of the nation’s capital of Port-au-Prince, reduced the many wood and masonry buildings to rubble, killing 200,000 and leaving an additional 1 million homeless.
Again, according to the Multidisciplinary Center for Earthquake Engineering Research, or MCREER, based at the University of Buffalo, The State University of New York, the frequency of earthquakes is not necessarily out of the ordinary. Modern day innovations have made it easier to monitor seismic activity and the occasional “clustering” of earthquakes creates a pseudo-trend. Population growth has resulted in densely populated urban areas, often without enough time to build the proper structures, let alone update seismic building codes, so when an earthquake hits these areas, it seems extraordinarily deadly. Furthermore, as a number of newspapers reported, wealthier nations can more easily prepare their buildings for the stresses of an earthquake, hence the extensive damage in Haiti.
Building codes in the U.S. were not frequently used until the 1970s on the West coast and even later on the East coast, says MCREER. Even then, because it was costly to retrofit old buildings with the newer standards, there was an emphasis placed on outfitting new structures to meet these codes while picking and choosing updates to make in the older buildings.
Furthermore, these codes vary across the country--buildings in Los Angeles are subject to more codes than those in Chicago, for example--and are based on earthquake hazard maps. And meeting these codes doesn’t necessarily break the bank on building construction; according to MCREER, it usually adds 1 percent to the cost of a home and 1 to 2 percent for commercial and industrial building construction.
Nonetheless, the recent score of earthquakes has provided an opportunity for increased dialogue about building codes and other protocol related to creating structures that will successfully handle earthquakes. With scientists and engineers predicting more extensive seismic activity for the western U.S., keeping structures relevant and capable of handling the stresses of an earthquake will be beneficial to the region – and the entire country -- in the long run.