Geology and Earthquakes

[Wrightwood]

[zelicaon]

L.A. May Be in for a Shaky Future

The scientists studying San Andreas activity near Wrightwood dug a series of trenches across the fault, then pinpointed locations in the trench walls where major earthquakes had clearly ruptured the surface in past earthquakes. They analyzed the organic material that had been buried over time and used carbon dating to determine the age of each rupture.

Geologists are now working to extend the record of earthquakes at Wrightwood back an additional 2,500 years.

http://www.wrightwoodcalif.com/ww1812quake.html

[raddog]

One of my friends lives in a house that sits right on top of the San Andreas Fault.  For those of you who don't know, the San Andreas Fault was made when the North American Plate moved over the Pacific Plate and split the continent in two.  San Francisco, L.A and San Diego are all on the Pacific Plate portion of California.  San Bernardino, Oakland, Indio, and Riverside are all on the North American plate side of California.  Disturbingly Wrightwood is split in two by the San Andreas Fault  Now scientists say that within a period of 50 million years the San Andreas will move north and Los Angeles will replace San Francisco as the neighbor to Oakland in aboujt 20 million years in about 35 million San Diego in 37 Tijuana and in about 50 million years the Pacific Plate portion of North America will completely split off from the North American part of California and move up towards Alaska.  Just thought you might want to know.

[clint]

Please, won't you help stop Plate Tectonics? Send your check or money order to....

[zelicaon]

Please, won't you help stop Plate Tectonics? Send your check or money order to....

No, thanks, not this time. I've already donated thousands of dollars to the Whittier Narrows "event".

[RennMan]

[raddog]

Thanks for the input, I had a basic idea about where the San Andreas Fault was but didn't quite have it right about where it actually was, what I do know is that the San Andreas Fault is actually the line seperating the Pacific Plate from the North American Plate.  In a couple of a million years L.A and San Francisco will be on the same landmass, the Sea of Cortez was actually formed from the moving away ol the Pacific and North American Pllates, at one time Baja California was connected to mainland Mexico and then the San Andreas Fault split and made the Sea of Cortez which is still widening today

[naturalist]

When the North American Plate overrode the East Pacific Rise in the miocene (or when was that--it's been a while since all my zillions of college geology classes!), all heck broke loose and the San Andreas Fault was born.  What I love is looking at relief maps of the western US-- Nevada looks like it has stretch marks--and that's pretty much what the basin and range is!  The East Pacific Rise (spreading center) goes right up the center of the Sea of Cortez, under the Salton Sea, and is under the continent in Nevada where there are basins and ranges and hot springs--high heat flow under the crust... I think it's interesting that when I visited the Yucca Mountain site for Nuclear Waste storage that they said how stable this area was, but it's over a spreading center!  Of course, geologic time is long, but plutonium half life is too.  But I don't want to get into politics here--just geology!  Too many exclamation marks!!!!  

[naturalist]

Sorry, I get a little excited about geology...

[WWRatOut]

And have you seen the Discovery Channel's documentary on SUPERVOLCANOES?  

That kept me sleepless for a few nights...    

Until I convinced myself it was pointless to worry about it!  

[naturalist]

[RennMan]

In my Geology class in Jr. College (and I won't say how long ago THAT was), we went over to Moss Beach, just after a good storm had washed away part of the beach.

There are some great tidepools there, and (at least according to my instructor), part of the reason was that Moss Beach is where the San Andreas goes into the water.  You can see some parabolic curves in the rock, where the original layers of deposits have been squeezed together over time.

I vividly remember looking at a part of the (really small) cliff, which had been washed away, and seeing a vertical line between one side and another, which more-or-less lined up with the bottom of the curves in the tidepools a short distance away.  We wondered at the time, whether we were seeing a manifestation of the San Andreas...

[Nolena]

We just went to Mammoth for the first time because our kid had a ski race there. It was a wonderful opportunity to explain why "smoke" was coming up from the ground. I had to phrase the explanation in 8-year-old terms. It was a way cool learning opportunity.  

[ChrisLynnet]

I'm not particularly concerned about living over the San Andreas fault -- earthquake faults number in the thousands throughout California, and any one of them could go at any time. And they do... I was living close by Whitter during the Whittier Narrows quake, and near Northridge during the '94 quake. I wasn't hurt but they scared me spitless.

Like the emergency people always say, be prepared to take care of yourself for quite while. Even in the large cities you never know -- after Northridge, a major water treatment plant was closed and much of the Valley and the Hollywood Hills had to travel to get drinking water.

[DudleyDoRight]

The first day of a class I was taking called ,"Natural Disasters", at UCI., we experienced the Whittier Quake at 7:37. The class began at 8:30. Needless to say the syllabus which began with volcanoes, was scrubbed. I am quite the student of seismologyand become "information central" when ther's any earth movement. Lucy Jones and Kate Hutton of the USGS are my idols.
The Dud

[easteregg]

Hey Matt Naas - where is Moss Beach? Sounds like an interesting look-see.

[RennMan]

Moss Beach and the Fitzgerald Marine Preserve are on the Northern California coast, about 10 miles north of Half Moon Bay, and 20 miles (or so) south of San Francisco.  Our son was there this past school year, on a oceans field trip, and had a great time!

Now that I'm finally looking at a good map, I realize that we were nowhere near the San Andreas Fault "line", but west of it.  The San Andreas trace goes into the ocean between SF and Pacifica.  San Andreas Lakes and Crystal Springs Reservoirs are more in the valley that the fault created.

Kinda like Wrightwood!

[HistoryBuff]

Calmast.org has maps showing many mountain community escape routes including escape from Wrightwood, Lytle Creek, San Bernardino Mountains, Crestline, Arrowhead, Big Bear and so on. Check it out! Signed, History (& esp. local geology) buff

[rpanic]

Has Anyone ever done a study of the hillsides around Wrightwood where the fault goes through. Just wondering how stable the hill is where the fault goes down Oriole Road.

[Nolena]

Here's a clickable fault map:

http://www.data.scec.org/faults/faultmap.html

And some other links that might interest you:

http://www.wrightwoodcalif.com/ww1812quake.html

http://www.wrightwoodcalif.com/forum/index.php/topic,3072.15.html

http://pubs.usgs.gov/gip/earthq3/