Posted on 04/14/2008 10:54:28 AM PDT by NormsRevenge
California - land of sun, beaches and earthquakes - faces an almost certain risk of being rocked by a strong temblor by 2037, scientists said Monday in the first statewide forecast of the seismic threat.
New calculations reveal there is a 99.7 percent chance a magnitude 6.7 quake or larger will hit the Golden State in the next 30 years. The odds of such an event are higher in Southern California than Northern California, 97 percent versus 93 percent.
The last time a jolt this size rattled California was the 1994 Northridge disaster, which killed 72 people, injured more than 9,000 and caused $25 billion in damage.
"It basically guarantees it's going to happen," said Ned Field, a seismologist with the U.S. Geological Survey in Pasadena and lead author of the report.
Despite the new results, scientists still cannot predict exactly where in the state such a quake will occur or when. But they say it should be a wake-up call for residents to prepare for a natural disaster in earthquake country.
"A big earthquake can happen tomorrow or it can happen 10 years from now," said Tom Jordan, director of the Southern California Earthquake Center at the University of Southern California, who was part of the research.
California is one of the most seismically active regions in the world. More than 300 faults crisscross the state, which sits atop two of Earth's major tectonic plates, the Pacific and North American plates. About 10,000 quakes each year rattle Southern California alone, although most of them are too small to be felt.
Knowing the likelihood of a strong earthquake is the first step in allowing scientists to draw up hazard maps that show the severity of ground shaking to an area. The information can also help with updating building codes and emergency plans and setting earthquake insurance rates.
The latest analysis is the first comprehensive effort by the USGS, SCEC and California Geological Survey to calculate earthquake probabilities for the entire state using newly available data. Previous quake probabilities focused on specific regions and used various methodologies that made it difficult to compare.
In the study, researchers computed the likelihood of a fault rupture using new information about where past quakes have struck, location of hard-to-spot faults and their slip rates as well as satellite-based GPS data of the Earth's crustal movement.
Scientists determined a Northridge-size shock occurs on average once every five years. The chance of a temblor that size striking the Los Angeles Basin is 67 percent compared to 63 percent for the San Francisco Bay Area. The San Francisco figure is similar to a 2003 analysis that put the probability at 62 percent. There is no past comparison that exists for Los Angeles.
Given California's seismic history, the new results should come as no surprise, said David Schwartz, a USGS geologist in Menlo Park who was not part of the study.
Researchers also calculated the statewide probabilities for larger temblors over the same time period. Among their findings: There is a 94 percent chance of a magnitude 7 shock or higher; a 46 percent chance of a magnitude 7.5 and a 4.5 percent chance of a magnitude 8.
Of all the faults in the state, the southern San Andreas, which runs from Parkfield to the Salton Sea, appears most primed to break, scientists found. There is a 59 percent chance in the next three decades that a Northridge-size quake will occur on the fault compared to 21 percent for the northern section.
The northern San Andreas produced the 1906 San Francisco earthquake, a recent disaster in geologic time compared to the southernmost segment, which has not popped in more than three centuries.
Scientists are also concerned about the Hayward and San Jacinto faults, which have a 31 percent chance of producing a Northridge-size temblor in the next 30 years. The Hayward fault runs through densely populated cities in the San Francisco Bay Area. The San Jacinto fault bisects the fast-growing city of San Bernardino.
You owe me a new screen!
Thanks for the info.
When the Northridge quake happened our pool whipped back to one end - and curled up and flew at the house coming into the room overlooking the pool and deck.
We didn’t live in Northridge but a few miles up the road...
That is as close as I want to get ever. Stupid me I had stumbled out of bed and ran to the back room to see all the hanging plants jumping up and down and I caught the water full face!
6.5 is no big deal.
A 6.5 under any US urban area is a disaster of immense proportions; Northridge (6.7) was deep, and much of its energy went in to fairly unpopulated areas; it also did 40 billion dollars worth of damage and would have killed hundreds if it wasn't in the wee hours of the morning.
A volcanic explosion deep underground which causess a vertical upheavel and a wave action radiating outward in all directions is the cause.
The above is abjectly false. What kook site did you get that from?
There is no horizontal movement in an earthquake.
There's plenty of vertical AND horizontal movements in earthquakes, measured by strong motion sensors.
The major damage is done to buildings on soft ground where the wave is unhindered rollong through the building lifting and droping sections in succession. On granit or hard rock formations the wave is dampened and damage is minor.
Well, the above is actually true, remarkably. You batted about 1-for-8 though.
There’s still a huge amount of older masonry buildings in both Southern and Northern California.
The real problem is that both Loma Prieta (distance from urban area) and Northridge (most energy directed away from LA) perhaps gave a false impression of how bad things will be.
Also, there were hundreds of buildings that LOOKED ok in Northridge that were later condemned due to structural damage - not every building is going to spectacularly collapse.
As the energy released by the rapid dislocation of mass travels through the adjacent strata, how that adjacent strata reacts is key to damage of structures placed on its surface.
If the strata is loosely consolidated, and lubricated by ground water, the basin acts like a bowl full of jelly, refracting and reflecting energy over longer periods of time. Rigid structures sitting on the jelly are literally shaken to structural failure. Accelerations are not as great as at the point of orgin, but the reciprocating nature of the motion destroys.
If the adjacent strata is hard rock, the energy transmitted is unmodified, except by distance. The structure sitting on the hard strata endures only a few sharp jolts without great motion displacements. A structure might be lifted sharply off it's foundation but the displacement is quick and short, limiting damage to cracks and small ruptures.
If everyone got right with Jesus, do you think he would call it off?
Oh goody, goody, goody. We live about 50 feet up and 300 yards back from the ocean on the northern California coast. This morning I heard a report that the “big” one was slated to hit 400 miles off the OREGON coast! Wish they’d get the stories straight, or maybe we’ll get real lucky and get it from both the south and the north.
Edgar Cayce predicted a huge megaquake for the EAST coast that would put CT, MA, RI and large portions of NY under the atlantic.
don’t feel alone;-) we’ll have to tie up the boat in Ohio.
We’ve heard it may snow here in New Hampshire next winter, too.
Yes.
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