July 30, 2010 | 2
When a magnitude 8.8 earthquake struck Chile on February 27, residents and seismologists knew it was a big one. But a new analysis reaffirms just how massive it was.
According to the new analysis, published online July 29 in Science, the rupture occurred along roughly 500 kilometers of fault line. After collecting data from 33 sites, a team of seismologists, led by Marcelo Farias, a geologist at the University of Chile, were able to take meter-by-meter measurements of the surface deformations.
Some places plunged as much as a meter downward and others were elevated at least two and a half meters. The biggest vertical thrust happened in the Arauco Peninsula, "where marine platforms emerged, shifting the coastline up to 0.5 kilometers toward the ocean," the authors noted in the new report. In the uplift area, researchers found dried algae and mollusks on dry land that had previously been submerged in the tidal area.
The February 2010 earthquake is the fifth largest on record since 1900, the seismologists noted. Chile also holds the record for the largest earthquake in the past 110 years. The May 1960 quake registered a magnitude 9.5 and killed more than 1,600 people—in addition to more than 200 reported dead from the resulting tsunami that traveled across the Pacific Ocean to Japan.
The scientists proposed that the February earthquake released much of energy that had been stored up since an 1835 rumbler in the region, which struck near the city of Concepcion and was noted by Charles Darwin in his journal from his second trip on the HMS Beagle.
As the South American and Nazca Plates continue to converge at about 6.8 centimeters a year along a lengthy subduction zone, however, another big one will likely strike the costal nation again some day.
Image of an uplifted marine platform with dried algae courtesy of AAAS/Science