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L.A. Heads For The Mountains

Forces in the Earth's crust are moving downtown Los Angeles toward the San Gabriel Mountains, possibly making the region more susceptible to earthquakes, researchers say.

The land in between is being squeezed like it's in a vise grip and the likely result will be more earthquakes and eventually a new mountain range. CBS News Correspondent Sandra Hughes reports.

"We've seen something very hard to see. The process of mountain building is always going on here in Los Angeles, and we've just now been able to install instruments that are sensitive enough to detect this over time," said geophysicist Mike Heflin.

Those instruments are called global positioning sensors that are placed all over Los Angeles. They receive signals from the global positioning satellites that orbit the earth. Scientists then measure how much the ground moves - one inch every five years in Los Angeles.

"We have evidence that there will continue to be earthquakes in this area related to the compression, but there's not specifics about exactly when or where in detail," Heflin said.

Compression contributed to the 1994 Northridge earthquake that caused $40 billion in damage and killed 57 people. And it formed the San Gabriel mountains. But there's no reason to panic. Mountains won't be springing up under people's homes anytime soon. It could be thousands, if not millions, of years for them to form. And experts still can't predict when the next earthquake will hit.

Using satellite surveying techniques, researchers found that downtown is edging toward the mountain range by about one-fifth of an inch annually. The crunched area or "shortening belt" responds by thickening, or slowly building up mountains.

"This probably means there's a greater likelihood of a quake inside this shortening belt than other places outside of it - with the caveat that this is over the next several hundred years," said the study's lead author, geophysicist Donald Argus of NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The study, published in the August issue of the journal Geology, sought to characterize the strains that might be released in large and dangerous earthquakes beneath Los Angeles, home to about 12 million people.

Such quakes would not be the "Big One" predicted on the San Andreas fault, which runs far east of the metropolitan area. Instead, the quakes would originate on smaller faults responsible for building mountains.

Such quakes would be slightly smaller than the predicted San Andreas shaker, but they could be just as deadly and damaging because of their proximity to urban areas.

Researchers found that a 3- to 25-mile-wide belt is being squeezed, including parts of the Ventura Basin, San Fernando Valley, east San Gabriel Valley and the area between downtown Los Angeles and Pasadena.

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