I heard about the Puente Hills Fault in the SCEC blog and its supposed to make a 7.3 quake in the future?
Feb 15, 2010
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Earthquake Questions
If this is true that Puente hills fault is supposed to make a 7.3 Landers Size quake from the San Gabriel Valley to Downtown LA. How come this isn’t well known in the US Mainstream Media like Hayward, New Madrid, San Andreas, Denali, Alaska Subduction, Denali, and the Cascadia are. Besides that LA and the rest of CA have so many Earthquake faults to investigate with.
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2 comments
Mark V on February 15, 2010 at 7:00 pm
Because it’s a thrust fault (a blind thrust fault, actually) that relies on compressional forces to function. This area of the world is a large transform boundary where the Pacific plate is grinding north relative to the North American plate. There just aren’t many compressional forces to build. In this case, such a fault would have a sequence of thousands of years between rupture.
Further, no one can predict earthquake rupture of any kind. Nowhere, no kind, not a tiny bit. Not even the Southern California Earthquake Center. Or the USGS. Nobody. We have no measuring equipment to nail down anywhere that strain is being built, and further, how much the rock can handle before a rupture.
The Puente Hills Fault has only had 4 major ruptures in the last 11,000 years!!
We here in Southern California have more geologic features than we know what to do with. The 1994 Northridge quake happened on another fault that we didn’t even know existed. It’s easy to find the big faults, or the big subduction zones, or the huge volcanoes — but locating hundreds of potentially dangerous faults of different kinds, nobody should bash anyone else for not having a perfect map. When I was growing up, there was a large earthquake along the Rose Canyon fault, and everyone thought it was a dead fault. We don’t know enough, and this SCEC paper doesn’t know *anything more.*
Beside, PHF is right under LA. What do you want people to do? Pick up and move? You can only prepare as much as you can reasonably prepare.
mandobob on February 15, 2010 at 7:00 pm
There are numerous faults, some named and others unnamed, in the LA area. Some have had paleoseismic investigations (evaluation of prehistory earthquake events and evaluation as to how strong they were based on things such as sediment offset) although most have not. There are even subsurface "blind" faults that have no surface expression. Most of these faults likely have had little or no significant evidence of significant fault movement, however, some of the more predominate faults have had investigations of prehistoric quakes and have been identified as having high potential for future damaging earthquakes. Some of these faults get a mainstream press attention, but most do not. It is impossible to predetermine or predict the magnitude, timing, or area that may be affected by an earthquake. All geologists can do is look at the previous quake evidence and determine the suspected probability that a particular fault will be responsible for a future earthquake. So the short answer to your 1st question is that no one knows although the fault has had significant movement in the past that might cause destruction to modern urban development. If you check with your local emergency response folks, they may have some more specific information on the probability of future large damading earthquakes in your area.