No, I haven't felt one yet. : ) I was just getting your attention! I've been reading up on them and have become more interested in them, especially after flying over the region a few times and being able to visualize the ripples in the land the sliding of the tectonic plates causes as well as being able to see faults from the air. There are also many speculations of our sea lions fleeing the docks at Pier 39, of which there were about 1,500 when I visited last, because "the big one" is coming. I became increasingly more interested, so here are the results of my internet research. : )
Quakes are happening all the time around fault-lines, just most are not felt. In fact, there have been several in the Bay Area just in the last week and a few within the last day. You can visit this webpage to see the United States Geological Society's latest mappings of earthquakes in the Bay Area and this webpage to see all in the US and world (this is an excellent website and fun to explore!).
Many of you are probably already more aware of the presence of earthquakes in this area than I am. I was only 6 when the Loma Prieta ("Dark Hill") quake that collapsed the Bay Bridge, the Cypress-Street Viaduct double-decker highway and portions of other highways (hwy 101 and I-280) I drive often. As many of you probably remember, the latest big quake occurred during the World Series between the Oakland A's and San Francisco Giants at Candlestick Park on October 17, 1989. The first few seconds of the quake were captured live on international television, with no substantial damage to the stadium or injuries resulting. Fans cheered the end of the 15 seconds of shaking ground and rippling wind-screen when it was over, not knowing the extent of the devastation they would encounter as they emerged from the stadium. The epicenter was 30 miles south of where I am currently living, near Loma Prieta peak. The damage extended from San Francisco and Oakland down to Santa Clara (my new home) and further south to Santa Cruz (on the coast). The quake resulted in 63 fatalities, 42 from the collapse of the Cypress-Street Viaduct double-decker highway in Oakland, and 3,757 injuries, of which only about 700 were serious. As a result, the double-decker highway was demolished and is now a single level highway and other highways were improved structurally to better withstand quakes in the future.
There are 8 fault-lines around the Bay Area: the San Andreas, responsible for the Loma Prieta and 1906 quakes, is filled with lakes and a reservoir which you can see from I-280 and traverses the SF peninsula; the San Gregario, which runs right by/through Half-Moon Bay; the Hayward fault, which runs through Oakland; the Calveras Fault, which stops short of Oakland to the south; the Rodgers Creek Fault, to the northeast of the Bay; the Concord-Green Valley Fault, to the NE of Oakland; the Diablo Thrust Fault, just south of the Concord-Green Valley fault; and the Greenville Fault, to the East of Oakland. With all of these fault-lines, there is a "63% chance for one or more magnitude 6.7 or greater quakes from 2007 to 2036" (www.earthquake.usgs.gov). The Loma Prieta was a 6.9. The earthquake of 1906 was a 7.8, lasting 20-25 seconds, with a slip or movement of about 20 feet horizontally, with the Pacific plate moving northward. The faults credited to having most potential for rupture and ability to cause damage are the San Andreas and the Hayward faults. The San Andreas fault is believed to have a 1906-type quake (with a slip of 20 feet or more) every 200 years. The Hayward fault is thought to produce a large quake (7.0 or greater) every 140 years, so the Hayward fault is thought to be the next source of a potentially devastating quake in the Bay Area.
My friend and I were discussing the quakes and all the disturbance about where our sea lions went when she picked me up from the airport. She said, "and with the next earthquake, isn't the peninsula supposed to fall off into the ocean???" I've been looking it up and couldn't find anything that states so, friend! YAY! The ground beneath Marina District in SF, built on the man-made landfill, is believed to have a very high potential for liquefaction (the soil becoming liquid-like during the quake as a result of the type of soil and materials beneath the surface), however, so maybe we should avoid the Marina District for the next 26 years?!
: )
My conclusions: 1. I miss the sea lions, but, I think they just went on vacation to San Diego and wanted to try their hand at out-swimming the Great Whites! (I think they just found them off the coast of Oregon, according to the BBC's website.) 2. The house I'm staying in was built in 1890 and has survived the 1906 and 1989 quakes, not to mention all the little 6.0's in the meantime, so I figure I'm good, even if it turns out to be haunted! 3. I live on the East side of the San Andreas fault and Coastal mountains, so the rest of yous on the west-side, good luck if/when the coast falls into the ocean (and I'll just throw in, if a tsunami comes from a quake near Japan--I don't foresee one overtaking the mountains . . . although it may come up from around the peninsula and through the bay . . . that should take some time, though, right? I'm a good swimmer . . . I'm good . . . right?); 3. Quakes only last 20-25 seconds and I like not knowing when they will hit! Much better than hiding in basements or flying around outside in really scary tornadoes!
I hope you are all doing well and weren't too bored by my dweeby post. : ) Pics of the new place coming soon! Be blessed and happy 2010!
Now for the improper citation of my sources:
http://en.wikipedia.org/wiki/1989_Loma_Prieta_earthquake (yes, I consider Wiki a scientifically reliable source!!!)
http://earthquake.usgs.gov/regional/nca/ucerf/ (this is a very neat website and will probably answer any question you have about quakes)
http://earthquake.usgs.gov/regional/nca/1906/18april/othereqs.php
http://seismo.berkeley.edu/outreach/faq.html (good faq sheet about quakes)
No comments:
Post a Comment