Skip to comments.Thrust fault quake, similar to south Asia, could happen in L.A.
Posted on 10/11/2005 8:14:30 AM PDT by Smogger
An earthquake of similar power to the one that devastated Pakistan is very likely along the section of the San Andreas Fault that runs from just north of San Bernardino down to the Salton Sea., That section of the 800-mile fault system is the one that is most locked, not having erupted since 1690. One scientist refers to it as the section that's "10 months pregnant." In contrast, it's only been 99 years since the northern section of the San Andreas caused the cataclysmic 1906 earthquake in San Francisco, the last "great" earthquake in California. The magnitude 7.6 earthquake that killed at least 20,000 people in south Asia on Saturday is about the size that scientists expect here.
"That would be comparable if the San Bernardino segment and the Coachella Valley segment slipped at the same time," said Sally McGill, a geology professor at Cal State San Bernardino who has extensively studied the San Andreas.
Such a quake could kill thousands of people and leave roads, pipelines and water systems a mess.
Modern building codes here would prevent the kind of devastation seen in Pakistan, but it would be a mistake to underplay the danger, experts warn.
While the San Andreas would need to rupture for 100 miles or more to generate such a powerful quake, a much shorter fault recently discovered under Los Angeles could cause the worst lost of life ever seen in a natural disaster in the United States.
A thrust fault, in which one huge block of the earth's crust pushes over the top of another block, is what triggered the Pakistan quake.
A similar fault, called the Puente Hills Fault, sits directly under Los Angeles. Scientists estimate it could generate a shaker up to a 7.5. Given it's right beneath downtown, as many as 18,000 people could be killed, according to projections by the Southern California Earthquake Center. Damage could hit $250 billion.
It was a thrust fault that caused the 1994 Northridge quake, still the most expensive earthquake disaster in the country, even though it was a relatively modest magnitude 6.7.
The good news is the Puente Hills fault is thought to pop loose every few thousand years, compared to the historical intervals of only a few hundred years for earthquakes along the San Andreas.
The San Andreas remains a pointed gun to the head of many Southern Californians, even those in Los Angeles, despite the fault's distance from that megalopolis.
And new research indicates the direction a fault rips can dramatically influence the intensity of the damage.
"When it breaks and ruptures, it sends energy out like it's out the end of a gun," said Thomas Jordan, director of the Southern California Earthquake Center.
Using supercomputers to create models for what would happen in a long rupture, the scientists have looked at various scenarios.
For example, if the rupture started near Indio or the Salton Sea and came northwest toward San Bernardino, it would be disastrous.
"Energy gets channeled through the soft basin sediments and gets blasted into Los Angeles," Jordan said.
San Bernardino also has its share of soil problems, including deep sediments in the Bunker Hill Basin, the area's underground aquifer. Liquefaction is a major worry in a large quake in which water-soaked soil becomes a loose muddy mess, unable to support buildings.
"If the fault ruptures from Cajon Pass south, Los Angeles doesn't do as bad, but Mexicali gets nailed," Jordan said.
In addition to the danger from soft, easily shaken soil, San Bernardino County has been one of the worst areas in the state for reinforcing or tearing down unreinforced brick buildings.
The reason earthquakes are so devastating in the developing world is because their buildings are largely made of unreinforced materials.
McGill, from Cal State San Bernardino, said nature has generated some powerful lessons in the past year, including the 9.0 Sumatra earthquake that launched the tsunami that killed an estimated 300,000 people, and Hurricane Katrina.
She's latched onto the issue of old brick buildings as one problem that can be solved before the next quake to save numerous lives. Cities should help retrofit them, or perhaps buy them and tear them down, she said.
"When I see what happened in Sumatra and with Katrina, and we could have predicted the level of damage ... I want to look forward to what we can do now to protect life," she said. "They are going to be deathtraps."
Perhaps it is time to buy western Nevada property in hope of having purchased ocean front land on the cheap? ? ?
Nothing new here they have been saying it could happen for a long time. It well or it won't.
So are you going to live in Costa del Lex, Luthorville, Marina Del Lex or Otisburg?
Otisburg? Otisburg.....I hear it is a little place.
I don't know if you've noticed or not but it seems like when a major quake occurs in one area a similiar one will occur on the opposite side of the planet within several weeks.
It's going to happen eventually and with tons of rubble on you ... you won't have to worry about a thing. You won't be here. Maybe it's time to relocate?
They're won't be much rubble around here. Most older homes are well constructed single story ranch style homes with a good foundation. Of course many of the new Mc Mansions that they build now on the side of hills are two story and built on cement slab by non-union workers so they probably won't fair so well.
That's what the Japanese thought until the Kobe quake that killed 5,000. Admittedly, the tile-roofed and wood-framed houses played a big role in Kobe but there were other problems (e.g., collapsing highway, collapsing concrete buildings, ground liquification, etc.) that could have caused a much bigger loss of life had the quake happened at a different time of day and that sort of thing could happen in California, too, especially to older buildings.
And just in the last few weeks, there was a large earthquake in South America...
Good gravy, man!
That's a nice way of saying that they are built by illegals.
That's a nice way of saying that they are built by illegals.
If the home builder has poured a foundation according to good engineering, it should not matter who the laborers were.
I say the best protection you can buy for an earthquake is DON'T LIVE THERE!! But, just like when the ice forms on the lake in the winter, no matter how many warnings of "stay off the thin ice" they announce, the ice fishing shacks go up because they best fish are always where the thinest ice is, so it's worth the risk. Someone always without fail falls through.
In L.A. the more years that pass without a major event, the higher the risk of being caught in one when it does. With all the events happening around the world lately, it just has to be playing on the minds of people who live there.
If and when it does happen, do you think owning the property next door is a good idea? Imagine the influx of refugees you will get seeking food and shelter. If L.A. gets totaly destroyed, that could mean millions. It would be ugly no matter how you look at it. I think the further away you are from it the better, although everyone in the nation would feel the impact economically no matter where you lived.