Posted on 08/21/2007 4:22:00 PM PDT by blam
Source: University of Oxford
Date: August 21, 2007
San Andreas Fault Likely Much More Destructive Than Current Models Predict
Science Daily — High-speed ruptures travelling along straight fault lines could explain why some earthquakes are more destructive than others, according to an Oxford University scientist. In this week’s Science, Professor Shamita Das suggests that ruptures in the Earth’s surface moving at 6km per second could make future earthquakes along California’s San Andreas fault much more destructive than current models predict.
A box canyon on the San Andreas fault: High speed ruptures travelling along the straight section of the fault could see Santa Barbara and Los Angeles worst hit in future earthquakes. (Credit: iStockphoto/Copyright William Royer)
Professor Das compared data from the 1906 California earthquake with data from a similar earthquake that occurred in 2001 in Kunlunshan, Tibet. The comparison suggests that, in both, the long straight portions of the fault enabled ruptures to travel twice as fast as the original ‘shear’ wave travelling through the rock. Such ‘super-shear’ waves were once thought to be impossible but could now explain why similar magnitudes of earthquake can cause much greater devastation in some areas than others.
‘Long straight faults are more likely to reach high rupture speeds,’ said Professor Das of the Department of Earth Sciences. ‘The fault starts from rest, then accelerates to the maximum permissible speed and continues at this speed until it reaches an obstacle such as a large ‘bend’. If the next earthquake in southern California follows the same pattern as the ones in California in 1857 and 1906, and in Tibet in 2001, a super-shear rupture travelling southward would strongly focus shock waves on Santa Barbara and Los Angeles.’
The 2001 Kunlunshan earthquake is of particular interest to scientists because it was so well preserved owing to its remote location and dry desert environment. Studies of the earthquake revealed telltale off-fault open cracks only at the portions where it was found to have a very high rupture speed. ‘These cracks confirm that the earthquake reached super-shear speeds on the long, straight section of the fault. This is the first earthquake where such direct evidence is available and it is exactly the kind of evidence that we do not have for the similar earthquake in California 1906, due to the heavy rains and rapid rebuilding that occurred there immediately afterwards.’
Professor Das believes that future research into rupture speeds could take scientists one step closer to predicting the potential impact of earthquakes in particular regions. She commented: ‘It appears that the 1857 and 1906 California earthquakes may have propagated faster than was previously thought. If this is the case then we need to apply the same analysis to other similar faults around the world. By developing a measure of the ‘straightness’ of faults and finding and recording evidence such as off-fault open cracks we hope to better understand these potentially devastating phenomena.’ The full article, entitled ‘The Need to Study Speed’, is published in Science on 17 August 2007.
Note: This story has been adapted from a news release issued by University of Oxford.
Argh....time to think about moving!
I wonder what they'll want us to give up in our lifestyles to prevent the "big one".
And miss the excitement???
Sounds to me you'll be moving, one way or another, even if you don't mean to.
I’m starting to think that whole chunk of California west of the fault lines will eventually collapse into the Pacific, but it won’t happen soon enough for the Democrats to blame it on Bush.
Women and minorities hardest hit!
Otherwise the Mrs. and the kids will be enjoying their new beachfront property without me.
I grew up in L.A.
The L.A. County Sheriffs are the toughest cop force I’ve seen.
When they started having practices for predicted food riots for after the big one hits I decided to leave.
There is NO food grown in the L.A. area. It is all trucked in.
The water comes from 400 miles north from a river called the feather river. If a real big quake hits and disrupts the water supply and a quake knocks out the freeway system, how ya gonna get food and water to those 20 or so million folks?
hmm previous models said it would be complete and utter destruction.... as opposed to this new model that shows ... utter and comple...er... um...
I, for one, am perfectly willing to give up Hollywood and all the moon-bats thereof. And I'm willing to contribute a dollar if the LA Times goes with it.
from the mormons...where else?
And they send their human fecal matter to Kern County.
They're gonna' be in a world of hurt, trapped in LA without what they need and with what they don't need.
We'll die at the hands of men. Probably well meaning idiots jack-booting along with the like of hillary......the Earth will do what it's always done.
Part of the year, the rest of the year it comes from the Colorado River.
There is a subtle difference between the supply that is able to make it past the water filtration systems and temporarily crash the yield in semiconductor manufacturing. I got in considerable trouble when I warned my boss to expect a 2 week yield crash when they switched. He kicked me out of his office when I made the prediction. Then called me on the carpet to explain what I did to cause the crash, and called me a liar to my face when I told him how I knew it was coming.
(He did call me years later to apologize when he realized it was true)...
Still, it’d be worth it just to see “Snake” Pliskin surf the
runoff.
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