SANTIAGO, Chile (CBS/AP) – Seismic experts say the 8.2 earthquake that killed at least six people wasn’t the long-overdue massive quake expected for the region.
Thousands of people evacuated from low-lying areas were returning home Wednesday after a spending a long night outside due to the threat of a tsunami.
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The U.S. Geological Survey initially reported the quake at 8.0, but later upgraded the magnitude of the temblor centered 61 miles (99 kilometers) northwest of Iquique. More than 20 significant aftershocks followed, including one of magnitude 6.2.
The quake was so strong that the shaking experienced in Bolivia’s capital about 290 miles (470 kilometers) away was the equivalent of a magnitude-4.5 tremor, authorities there said.
But Tuesday night’s quake, which would have been the 2nd largest ever to hit the lower 48 states if it struck along our coast, was not the big one seismologists are expecting.
“Could be tomorrow, could be in 50 years; we do not know when it’s going to occur. But the key point here is that this magnitude-8.2 is not the large earthquake that we were expecting for this area. We’re actually still expecting potentially an even larger earthquake,” said Mike Simons, a seismologist at the Geological Survey.
Chile is one of the world’s most earthquake-prone countries because just off the coast, the Nazca tectonic plate plunges beneath the South American plate, pushing the towering Andes cordillera to ever-higher altitudes. Nowhere along this fault is the pressure greater than in far northern Chile, an area known as the “Iquique seismic gap”.
The USGS says the seismic gap last saw a major quake in 1877, when a magnitude-8.8 quake hit. Another quake of similar force hit just north of the area in 1868
“This is the one remaining gap that hasn’t had an earthquake in the last 140 years,” said Simons. “We know these two plates come together at about 6, 7 centimeters a year, and if you multiply that by 140 years then the plates should have moved about 11 meters along the fault, and you can make an estimate of the size of earthquake we expect here.”
The latest activity began with a strong magnitude-6.7 quake on March 16 that caused more than 100,000 people to briefly evacuate low-lying areas. Hundreds of smaller quakes followed in the weeks since, keeping people on edge as scientists said there was no way to tell if the unusual string of tremors was a harbinger of an impending disaster.
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