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Report: Mountains grew a foot in Calif. quake

LOS ANGELES, California (Reuters) --California's largest earthquake in four years struck on Monday, causing planet Earth to ring "like a bell" and mountains to grow a foot (30 cm) taller, geologists said.

The magnitude 6.5 quake hit near the coastal city of San Simeon almost exactly half way between San Francisco and Los Angeles, setting high-rise buildings swaying in both cities.

Earthquakes relieve pressure between clashing continental plates. The plates float on the earth's mantle, which has a putty like consistency and moves as the earth's core heats it.

On Monday one piece of crust shoved beneath another about 4.75 miles (7.6 km) beneath the surface of the earth and at the intersection of the Pacific and North American plates, U.S. Geological Survey seismologists said

That sent tremors along America's west coast and beyond.

"For an earthquake this size, every single sand grain on the planet dances to the music of those seismic waves," Geological Survey geologist Ross Stein said Monday at a news conference.

"You may not be able to feel them, but the entire planet is rung like a bell."

The Monday earthquake struck on what is believed to be the San Simeon thrust fault. Pressure in a thrust fault is relieved when one piece of earth pushes up on top of another, compared with lateral faults -- like the famous San Andreas -- in which two piece of crust slide next to one another.

Thrust faults produce mountains, and the San Simeon quake probably improved the view from the nearby hills, Stein said because, "mountains have probably been pushed up about a foot or so by this earthquake."

The tremor was the biggest in California since 1999, when the Hector Mine quake crashed through the desert east of Los Angeles, and it packed about half the power of the Northridge earthquake which shook Los Angeles a decade ago.

Earthquake power is measured on a scale which increases exponentially, so at 6.7 the Northridge quake was about twice as powerful as the 6.5-magnitude San Simeon quake.

The Northridge quake was also one of the costliest disasters in U.S. history, causing over $40 billion of damage since it shook a heavily populated area.

Geologists expect smaller aftershocks of magnitude 5 to continue for days, weeks and longer, and there is a 5 percent to 10 percent chance that Monday's quake was a precursor to a bigger one.

The plates have created a patchwork of faults, said Susan Hough, a seismologist at the United States Geological Survey in the Los Angeles suburb of Pasadena.

"The crust is getting mangled over a zone," she said. "As the plates move they are sort of grinding California into ribbons," she said.

Eventually the movement will carve Mexico's Baja California, the peninsula that juts south below San Diego, California, off from the rest of Mexico.

But California is not going anywhere quickly.

From a geological perspective, the area has looked about the same for 5 million years, Hough told Reuters.

"We are not falling into the ocean," she said.



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