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Magnitude 6.0 Quake Hits Northern California, Causing Injuries and Outages 135

Posted by timothy
from the be-safe-out-there dept.
As numerous sources report, an earthquake of magnitude 6.0 struck California early Sunday morning, with an epicenter about 9 miles south of Napa. According to the San Francisco Chronicle's account, Some power lines down in western Contra Costa County, but Bay Area bridges appeared to be fine, according to the California Highway Patrol. There were widespread reports of power outages, gas leaks and flooding in the North Bay, with at least 15,000 Pacific Gas and Electric Co. customers without power in Vallejo, Napa, Rohnert Park, Santa Rosa and Sonoma. Police reminded motorists to stop at darkened intersections. ... In Benicia, several miles from the epicenter, the quake was strong enough to knock pictures off mantles. Bay Area bridges appear to have survived the quake -- significant, in that the L.A. Times reports that USGS estimates peg it as "the largest earthquake to strike the Bay Area since the Loma Prieta temblor of 1989," and says that injury reports (especially from glass) are streaming in from the area around Napa. The Times also has a larger estimate of customers suffering power outages: "more than 42,000" around the northern Bay Area. Unsurprisingly, social media channels are full of pictures showing some of the damage.

For those in California, did you feel the quake? (And from how far away?) Update: 08/24 13:15 GMT by T : Also in earthquake news: an even stronger quake (magnitude 6.4) on Saturday struck central Chile, shaking Santiago -- nearly 70 miles from the epicenter -- for more than half a minute, but with "no immediate reports of fatalities or serious damage."
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Magnitude 6.0 Quake Hits Northern California, Causing Injuries and Outages

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  • Report from SJC (Score:2, Interesting)

    by Anonymous Coward on Sunday August 24, 2014 @09:39AM (#47741547)

    It woke me up.
    IMO a 6.0 in the Bay Area should go down almost unnoticed (like it does in prepared countries like Japan), instead of creating outages, floods, etc...

  • by kanweg (771128) on Sunday August 24, 2014 @09:49AM (#47741577)

    Join the Quake catcher network of Stanford. You can order a sensor, but your laptop can detect them too.
    http://qcn.stanford.edu/ [stanford.edu]

    The detected earthquake
    http://qcn.stanford.edu/earthq... [stanford.edu]

    Bert

  • by brainboyz (114458) on Sunday August 24, 2014 @12:59PM (#47742353) Homepage

    Because you can feel the relative strength where you are. Also, you start to get a feel for how far away it is based on the motion. Close ones rock'n'roll at the same time, while further ones get a jolt or two followed by a rolling motion.

    It's part of the SoCal culture/tradition, so Independence Day had it right.

  • by Ungrounded Lightning (62228) on Sunday August 24, 2014 @02:23PM (#47742653) Journal

    "Why do Californians think they can "feel" the strength of a quake? It's complete nonsense because you cannot feel its distance."

    It's not nonsense at all. Bigger quakes last longer. The duration of the shaking is a good measure of the actual strength, and can be read directly off the seismographs, while more accurate estimates take a while to compute from these and other measurements.

    That's why you see initial estimates as "duration magnitude [wikipedia.org]", later revised to "moment magnitude" which more accurately measures the energy from measurements of the distortion of the underground structures due to the stress changes. You'll notice that it's SO good that the adjustment is usually only a couple tenths of a scale point - less than a 2:1 difference in energy.

    The rip starts at some point along the fault and propagates along it in fits and starts, much slower than the compression and shear waves from the individual releases, as the motion from the relaxing stresses in the section that let go increases stresses in the next section. This keeps up until the effect reaches a point where the stress isn't enough (at the time) to make it let go. (You get aftershocks when the more gradual readjustments add "straw to the camel's back" and get it going again - or start one on another nearby section or another nearby fault.)

    The strength of the wave decays with distance. But the duration increases as the wave takes multiple paths, scattering off underground structure. So a distant earthquake doesn't "feel" shorter than a nearby one. Longer-but-weaker. Also, the P wave propagates much faster than the S wave, is weaker, and doesn't "stretch out in time" much at all. Time separation is greater with distance. They feel very different. (Mnemonic: First the P wave makes you pee, then the S wave ...) So with enough experience one could ballpark both the strength and the distance from the feel of the quake.

    For instance: Loma Prieta, a 7.1 moment magnitude (6.9 early duration magnitude estimates), propagated along aobut 22 miles of fault. It lasted 8 seconds, though as you got farther away the shaking got up to 45 seconds before it became too weak to be noticed. I was standing in front of Palo Alto City Hall when it got there, and my perception was first (P wave) "a truck is going over this overpass - wait', I'm not ON an overpass", then (S wave) "being in an airplane experiencing 15 seconds of mild turbulence." (Most ground-bound constructions {except for mobile and modular homes, which are built to be shipped on highways}, weren't built to withstand "15 seconds of mild turbulence". B-b ) I was listening to a San Francisco radio station: Seconds after the shaking started, the announcers got in two sentences (first about feeling an earthquake (P wave), then that it felt big (start of S wave)) before the transmitter failed (a bit into the S wave) - and the shaking was far from over.

    The scale is logarithmic base 10, so a 1 point difference in scale is a 10x difference in energy, and thus time. This makes it EASY to guess the magnitude (if your sense of time doesn't distort to much from the excitement). A 6.1 would be 1/10th the energy of Loma P., so also about 1/10th the time, and Nappa to Oakland is comparable to Loma Prieta to Palo Alto, so call it a second and a half of the strong shaking.

    On the other hand, for the first quake I felt after moving to CA I was nearly on top of a small one. (I think it was a high 2.x or a low 3.x.) Very sharp single shock - like a car hitting a concrete building while you're inside - followed by "echoes" as the wave moves on rapidly and EVERY building makes the sound of being hit (followed by a chorus of car alarms - shock sensors were common then). Sensation: Being in an elevator when it hit a misaligned section of the guide track. Three-stage perceptual distortion, as I realized that I was standing on the ground and my brain momentarily remapped my mo

  • by bill_mcgonigle (4333) * on Sunday August 24, 2014 @03:18PM (#47742955) Homepage Journal

    We're worried about 90% of life on Earth becoming unsustainable as a result of global warming.

    No we're not - we have fossil records from, e.g. the Jurassic where high temperatures and CO2 at about 1300ppm resulted in mega- flora and fauna all around the earth, even in areas that have desertified as the Earth's moisture has become locked up in Antarctic ice sheets over the past several hundred years of cooling (as evidenced by ancient Chinese maps).

    What "we" are worried about is the rich cultural and political elite losing their seaside mansions and other shore-line real estate investments. Because we can find seashells 15' underground 20 miles inland from them and we know that the Earth's climate oscillates on several timescales, it's inevitable that the Earth will return to those prior conditions at some point in time.

    But if we can slow down the encroachment of the sea on the banksters' wealth at all, then it's worth any cost to be borne by the 99%.

"Who cares if it doesn't do anything? It was made with our new Triple-Iso-Bifurcated-Krypton-Gate-MOS process ..."

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