Seismologists Say Chile Could See Another Big Quake Soon
March 27, 2011 • 11:20AM

Both Chilean and foreign seismologists, geologists and engineers warn that another big earthquake in Chile, of a magnitude as high as 9 on the Richter scale, is a real possibility in the near future. In the two weeks since the Japanese quake and tsunami, there has been a considerable amount of seismic activity in Chile, although not of a magnitude to cause significant damage.

But Stefano Lorito of Italy's National Institute of Geophysics and Vulcanology reported in late January of this year that Chile's Pacific coast is a likely site for a new earthquake, due to the fact that the 8.8 magnitude quake that occurred on Feb. 27 of 2010 didn't relieve seismic stress that had been building up in the zone. According to Lorito's study, which was published Jan. 30 in Nature Geoscience, the 2010 quake in south central Chile had only partly broken stresses deep in the Earth's crust in an area south of the capital of Santiago. These stresses have been building up since an 1835 quake devastated the city of Concepcion, also severely damaged in last year's quake.

Lorito's team of scientists looked particularly at the risks in an area known as the "Darwin Gap" on the coast near the city of Concepcion, so named because Charles Darwin was visiting the area and documented the enormous damage done to that city by the 1835 quake. Examining data from tsunamis, satellites and other sources, Lorito's group found that a continental Nazca plate beneath the Pacific Ocean was sliding under the South American mainland at a rate of about 6.8 cm. (2.7 in.) a year, so that a total of almost 12 meters (39 ft. 4.4 in.) of stresses had built up since 1835.

While the area deep below the earth to the north of Concepcion moved almost 20 meters as a result of the 2010 quake, the Darwin Gap area barely moved. Lorito's team concluded that "the increased stress on the unbroken patch may in turn have increased the probability of another major to great earthquake there in the near future."

In 2007, a study done by a group of experts from France's Institut de Physique du Globe, the Geology Laboratory of the Ecole Normale Superieure in Paris, the University of Chile's Geophysics Department, and the Bulgarian Academy of Sciences identified the Darwin Gap as a "mature seismic gap" which "in a worst case scenario...already has a potential for an earthquake of magnitude as large as 8-8.5, should it happen in the near future." The February, 2010 quake was 8.8 on the Richter scale.