Menlo Park USGS studying Chile quake event

February 28, 2010 11:38:15 AM PST
Earthquake experts at the U.S. Geological Service in Menlo Park were not surprised by Saturday's 8.8 earthquake in Chile, but they are certainly studying it closely.

Chile is even more prone to earthquakes than California. They are more likely to have larger ones there whereas experts would not expect to see an 8.8 earthquake in California. It is because of the Nazca plate which is shoving itself underneath South America.

"This is an area that very frequently, causes extremely large earthquakes and from that standpoint, this is no surprise," said geophysicist Ross Stein. "This is an area that we would have expected to have large earthquakes on a regular basis."

Geologists say Saturday's quake was about 500 times larger than the earthquake that happened in Haiti last month. But, experts say Chile is better prepared and that is why the death toll is much smaller than in Haiti.

"That's a very positive message for everybody who lives in earthquake country, that we can prepare, and there are ways of designing structures that will not kill people when a great earthquake occurs," Walter Mooney said.

Chile did experience some massive damage. The earthquake was not only powerful, it also was not too far from the surface.

"This is not a very deep earthquake, what we would call a 'shallow subduction zone earthquake,'" Mooney said. "So, the measure of safety that's provided is not that significant in this case."

Geologists will now be watching closely for aftershocks. There have already been more than 40. They predict people on the outskirts of the quake are at risk, but earthquake-prone areas around the world should be OK.

"It hasn't really shifted our faults or increased the pressure on any of our faults," Mooney said.

The scientists are also interested in the tsunami the quake triggered. The point they want to emphasize is that people should never try to see a tsunami.

"By the time a tsunami gets on shore and is moving anywhere from 20 and 40 mph, the rule of thumb is if you see a tsunami it's too late to outrun it," Mooney said.

Two key factors helped create the tsunami. First, the quake happened underwater, off the coast of Chile. Secondly, it also occurred on a thrust fault which creates vertical movement and shoves water upwards.