How will a San Andreas Fault earthquake affect Los Angeles?

4 comments

1. 

   Mark V on January 5, 2010 at 2:12 pm

   That depends on if you’re built on strong bedrock, or sediments, the proper integrity and "earthquakeproofness" that was built into your structure, distance to the fault, magnitude of the earthquake, whether or not you have an isolation system, and so on.

   First, you always want to build on good, solid bedrock. Sediments will shift and even amplify surface waves, and have the even more dangerous potential for liquefaction – the sediments literally begin to act like a rather thick liquid; perhaps like Hershey’s chocolate syrup. Bedrock will shake, of course, but will handle the surface waves better, as it will be less apt to allow significant flexing. Look at the damage map of the 1906 San Francisco Earthquake to see how bedrock stood up to sediments (obviously don’t count the areas later destroyed by the fires).

   Do not build your structure out of brick-and-mortar or concrete block. This is bad. Your home should be built from steel, ideally. Not massive I-beams and girders, but reasonable home-quality steel framing. The vertical frames should be cross-braced, and very careful attention paid to the joints, which are the weakest parts. They need to be strong enough to hold the framing together in a sturdy fashion, but loose enough to be able to shift with the earthquake, instead of just trying to take it as on giant bang against something rigid (I visited my grandfather in one of the highest floors of the TransAmerica building back in uh.. hmm.. 1986 or so – earthquake came, and we swayed about 30 feet from side to side – sometimes soft is better than rigid, somewhat like "negative-acceleration").

   Don’t use excessive glass, either necessary or decorative. Same with bricks. Glass can shatter, and bricks can fall, sort of a "secondary" effect of an earthquake. In fact, the most common damage in any normally-large earthquake that we get down here is simply glass breaking and chimneys falling over.

   You obviously can’t control the size of of the earthquake…

   A seismic isolation system (SIS) is either a passive or active system that is placed beneath your foundation, that allows the structure to move and sway as a whole system, and they do a very good job of essentially negating all but the largest earthquakes – the ones that simply overpower the SIS. Sometimes these are simple passive springs and sheets of ball-bearings, sometimes they are active pneumatic or hydraulic cylinder systems so complex that they look like the ones used in motion-controlled flight simulators.

   However, nobody can build anything to perfection, and a very large earthquake can bring down anything that it wants to. Some of the worst earthquake effects come from broken water mains and gas lines. Electric lines can also be cut. All of this results in a bit of chaos, and especially all combined, can result in large fires, with which there is little to no water to fight. San Francisco found this out twice in the previous century. First in 1906, where the fires ripped through the entire city unchecked, as the water mains had been broken. Second in 1989, the Loma Prieta earthquake. Again, the mains were cut, and fires started in a number of places, most importantly, the Marina District. The Marina would have been burnt to a crisp, but one fireboat managed to push its way over a sandbar and right up to the wharf. It pumped out enormous amounts of water directly from its nozzles before the SFFD (along with hundreds of local volunteers) managed to get large hoses to the boat, where they carried the water further inland. By the time the water was completely put out, the little boat had blown out more than 100 million gallons of water. I’m not exactly sure, but I think it’s a floating museum today.

   During the Northridge quake, there were some deaths, and some destruction, but surprisingly few, giving the magnitude and ground movement recorded by the USGS and seismometers at USC, UCLA, and other stations here in Southern California. Only 57 died.

   Check out the link below for more detailed information about another earthquake that could be reasonably expected to hit the area.

   I personally don’t believe in the theory of The Big One shattering So. California. Not that it’s impossible, just that I consider it unlikely, just because of the way that all of our microplates are constantly shifting around under the San Andreas’ influence.

   But be prepared, you never know. Go through the time to make a proper earthquake preparedness kit, if you haven’t already, and arrange a singular meeting point, because there may be no communication, and you can’t all go wandering around looking for each other like bad Hollywood movie.

   1994 northridge

2. 

   Greg on January 5, 2010 at 2:12 pm

   A giant earthquake can affect places very far away- the affects of a san andreas earthquake have been felt in michigan. LA would definitely be in trouble if a large scale quake were to occur- it’s pretty close to the fault line.

3. 

   Bob Saint Louis on January 5, 2010 at 2:12 pm

   If it’s large enough, it would probably improve it. Sort of like city wide slum clearance.

   RRR

4. 

   ProTon 【ツ】 on January 5, 2010 at 2:12 pm

   The San Andreas is a classic “Strike Slip” fault: the two sides (for the most part) move past each other horizontally.Located at the boundary between the Pacific Plate and the North American Plate.

   Los Angeles is subject to earthquakes due to its location in the Pacific Ring of Fire. The geologic instability produces numerous fault lines both above and below ground, which altogether cause approximately 10,000 earthquakes every year. One of the major fault lines is the San Andreas Fault , it is predicted to be the source of Southern California’s next big earthquake.

   Major earthquakes to have hit the Los Angeles area include the 1994 Northridge earthquake, the 1987 Whittier Narrows earthquake, the 1971 San Fernando earthquake near Sylmar, and the 1933 Long Beach earthquake. Nevertheless, all but a few quakes are of low intensity and are not felt. The most recent earthquake felt was the 4.7 2009 Inglewood earthquake on May 17, 2009. Parts of the city are also vulnerable to Pacific Ocean tsunamis; harbor areas were damaged by waves from the Valdivia earthquake in 1960. The Los Angeles basin and metropolitan area are also at risk from blind thrust earthquakes.
   how badly would Los Angeles be affected if an earthquake hits ? We cannot predict the damage , it depends on the intensity of the earthquake and/or tsunami …an earthquake measuring 8/9 on richter scale can bring great destruction .But with good disaster management mechanism the scale of the destruction can be reduced to a great extent .

   http://neic.usgs.gov/neis/gifs/ca_plates.gif
   http://www.planetware.com/i/map/US/san-andreas-fault-map.jpg
   http://www.nasa.gov/centers/jpl/images/content/115901main_map-la-browse.jpg
   http://www.lonelyplanet.com/maps/north-america/usa/los-angeles/map_of_los-angeles.jpg