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Newly Discovered Fault Under L.A.
Randolpho writes "Whether you like the city or not, you can't say Los Angeles doesn't have a fault. It does, and it's one of earth-shattering proportions. Geologists have confirmed that LA was built right over a faultline, which they're calling the Puente Hills Blind Thrust System; it runs from northern Orange County through Los Angeles on up to Beverly Hills, and has a habbit of ripping earthquakes as large as 7.5 on the Richter Scale every 10 thousand years or so. And the last one was about 8 thousand years ago."
CNN has an article on this new fault that is slightly less confusing. You can find it here.
Impersonating Tycho from Penny Arcade since before there was a PA.
This is silly - if not FUD for grant money.
The LA basin is about 1 to 30 kilometers of rubble on top of a very active basement of solid rock which is riddled with active faults like a piece of dropped china is riddled with cracks. All of the rubble (alluvium) makes it hard to see active faults as they are buried deep.
Basically every big earthquake that LA has experienced (with the exception of the large one the San Andreas fault in the 1840's) has been on a previously unknown fault.
So, earthquakes happen, but our ability to tell exactly where they will be is near nil.
>The only thing of note is that this puts to rest the thought that blind thrust faults cannot exist
I don't think the existence of blind thrusts has ever been a question. Structural geologists have been quite aware of that type of structure for some time. Indeed, the question isn't even if blind thrusts are a seismic problem -- the Northridge earthquake in 1994 was on a blind thrust. The problem with blind thrusts is that there is no easy way to tell where they are, principally because (by definition) they don't "daylight" i.e. reach the surface. The cool thing about this study is that paleosiesmologists have documented a previoiusly-unknonwn blind thrust fault in an urban area (a major seismic hazard) using well data and geophysics. Not only that, but they mananged to place constraints on it's prior movement history and its recurrence interval. A nice piece of important work.
Mike Davis's book, Ecology of Fear: Los Angeles and the Imagination of Disaster,is a pretty good liberal read about LA and its various geological and meteorological issues. You might also check out his City of Quartz as well if you really hate the place :-)
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Winton
It could be worse: it could be Seattle (an earthquate caused by Juan de Fuca plate movement could cause a Tsunami AND erupt that little ol' volcano they have just outside the city).
Not to mention the potential strength of the next "Big One" in the Seattle/Vancouver area. 8 Million people, suddenly swimming...
The Cascadia Megathrust Event is due.
Fascism should more properly be called corporatism, since it is the merger of state and corporate power.
These are maps showing magnitude, fault, date, and so on. You can also view "shakemaps" and other cool stuff.
NEIC real-time list
Los Angeles area seismicity map
U.S. seismicity map
World seismicity map
I heard exactly this same sort of story when I was living in downtown LA and the Whittier Quake happened (6.1 on the Richter scale IIRC). I wonder when that was, hmm.. must've been around 85 or 86? They said the Whittier Fault had the same potential to liquify the downtown subsoil. When it hit, I was in an unreinforced brick building just a couple of miles from the epicenter, I couldn't believe how much the ceiling beams shook, I thought the building was about to collapse. But anyway, I wonder just what is the big picture, there are a other newly discovered faults like the Whittier fault right through the downtown area, that's probably how that area originally became the flatter LA basin area, due to the repeated liquefaction of soil during quakes and subsequent resettling.
Actually, LA takes as many seismic precautions than any other metropolis in the world (probably equalled only by Tokyo). Evidence of this is that the only apartment building to actually collapse in the Northridge 'quake had serious code problems. Scores more were rendered uninhabitable, but among apartment buildings only the Northridge Meadows complex pancaked; it was later discovered that it had been built without some of the required reinforcing between floors. Most of the rest of the country has no such requirements, and under the building codes in, say, St. Louis, you would have had dozens of Northridge Meadows.
The problem with the Puente Hills fault is that it goes right under downtown. Although the buildings there are designed to withstand a large earthquake on more distant faults, they weren't designed for a Northridge-style event right under them. (Northridge was 6.8 Richter, more or less the size of event expected on the Puente Hills fault.)
I lived around a mile from the Northridge epicenter, in West Van Nuys. Real Estate values in our neighborhood went down briefly, and didn't start climbing until a year and a half later. But the market hardly colapsed. (It helped that the houses in our area were well-built, with only those with second-story add-ons suffering much, if any, structural damage.) Nobody I know moved to Phoenix. When we sold our house four years later, we got what we expected for it, around 20% more than its valuation shortly before the Northridge quake occured.
Why do I always hear "This earthquake (or another) strikes every 1000 years". Earthquakes are not that predictable. So, no, the eathquake will not be there in 2000 years, it could be thera ANYTIME. No one in history has ever predicted an earthquake with a sufficient notice. I wonder when they will let go of the old geologists fantasy of "earthquake prediction".