I Feel The Earth Move Under My Feet....

California is earthquake country, and just last week we had a little reminder that the ground we live on here is constantly trying to go somewhere else. The 4.6 earthquake that hit the Chatsworth area at 1am woke up some folks and shook a few things off shelves, but I didn't feel a thing (though my son was still awake and heard the house make a funny noise as the seismic waves passed by).

Cal Tech scientists are constantly warning us that we're due for a big one:

While 300 miles of the northern fault ripped in 1906, killing an estimated 3,000 people in San Francisco, and the middle part shook during the powerful 1857 Fort Tejon earthquake, the southern section of the fault hasn't popped since the late 1600s.

There were six earthquakes in the 900 years before that, and none in the past 300, Jones said, meaning the most devastating disaster in 100 years is long overdue.

That's why scientists got funding last year to study a potential magnitude 7.8 quake that would originate near the Salton Sea and race 200 miles up the fault to Lake Hughes, just west of Lancaster.

What has surprised scientists is the level of destruction the earthquake would cause in Los Angeles, even though the fault is 60 miles away. ...

That's about the same distance San Francisco was from the epicenter of the 1989 Loma Prieta earthquake. That magnitude 6.9 quake knocked down a freeway, severely damaged the San Francisco-Oakland Bay Bridge and killed 63 people.

A 7.8 quake would shake nearly 10 times harder.

And it would shake for minutes. The magnitude 6.7 1994 Northridge quake lasted only seven seconds but killed 60 people.

"The calculations of motion on a San Andreas earthquake surprised us with longer term motion than we expected," said Tom Heaton, a professor of engineering seismology at Caltech. "I think people will be unpleasantly surprised by how hard the shaking is."

Even though the shaking in Los Angeles wouldn't be as intense because of the distance, the city sits on a deep basin of sediment that will shake like a bowl of gelatin and prolong the event.

"There will be large low-frequency waves. The ground will shift 10 or 20 feet. The (high-rise) buildings will resonate back and forth, and the slow part of the ground motion is important to them," Heaton said.

Some researchers think it's possible some skyscrapers could collapse.

This really isn't breaking news. I was teaching this stuff to my bank employees back in the early 90's when we did our emergency training. Although the southern San Andreas has the greatest potential for a sudden break, the central area around Fort Tejon (between Los Angeles and Bakersfield) has historically had a major earthquake every 130 years. The last one was in 1857. That baby's ripe to go.

Earthquakes are part of life around here, though we haven't really had a good one since the Northridge quake in 1994. There were several strong quakes in the years prior to that, with major events in 1987 and 1992. Unfortunately, around here there are no sirens or Weather Channel warnings when the next one will hit. It's anybody's guess.