To consolidate, disseminate, and gather information concerning the 710 expansion into our San Rafael neighborhood and into our surrounding neighborhoods. If you have an item that you would like posted on this blog, please e-mail the item to Peggy Drouet at firstname.lastname@example.org
Tuesday, February 18, 2014
Another Reason For California To Be Scared Shitless: Earthquake Storms
Peggy Drouet: Note that the Raymond Fault is mentioned in the article. This is one of the faults that the 710 tunnel would cross.
A 3D rendering of the San Andreas Fault by NASA/JPL
Worrying about the Big One is so passé. What you should really
be worried about are the Big ONES. Yep: chances are, it won't be a
single large earthquake that takes California out, it will be multiple,
large earthquakes. Or perhaps you'd prefer to use the official Sharknado-esque term: "earthquake storms."
Here is a
plot befitting a Michael Bay movie in development: A quake on the San
Andreas Fault could trigger a domino-like effect that will unleash the
power of SEVERAL MORE EARTHQUAKES on SEVERAL DIFFERENT FAULTS as
multiple paths of destruction ripple their way toward dozens of densely
populated metropolitan areas.
half-century ago, it was Stanford professor Amos Nur who first noticed
the evidence of a phenomenon he called "stress transfer" when studying
ancient earthquakes. Here's one way Dvorak says to visualize it:
that a giant zipper is holding together two tectonic plates. As the two
plates tug against each other, a segment of the zipper suddenly slides
open, but, as a zipper is apt to do, it snags occasionally. As the
tugging continues, the zipper again slides, then snags again. Each time,
the sliding zipper represents an earthquake and the tugging of the
plates becomes concentrated at another place along the zipper.
consider another example—one that Nur prefers. Take a wide rubber band
and cut a few short slits in it. As the band is stretched, each slit in
turn opens up and the ends of the slits lengthen. The sequence that the
slits open and by how much depends on how the stress pattern gets
transferred and concentrated at new locations across the rubber band.
of the single, catastrophic event followed by the period of relative
stability that we usually think of when our tectonic plates let off some
steam, Nur started looking for evidence of series of earthquakes
traveling along a fault over a period of decades. He first found it in
the ancient city of Mycenae, where this kind of earthquake storm might
have been responsible for the abandonment of several Mediterranean
societies, triggering the end of the Bronze Age.
was even more contemporary evidence in Turkey: a series of seven
earthquakes erupting one after another along a 600-mile-long segment of
the North Anatolian Fault:
1939, after two centuries of quiescence, the North Anatolian Fault,
which runs across northern Turkey roughly parallel to the coastline of
the Black Sea and which is a boundary between the African and Eurasian
plates, came to life. By 1999, 13 major earthquakes had occurred. What
is even more remarkable, 7 of the 13 ruptured the North Anatolian Fault
in a systematic way: Each successive earthquake ruptured a segment of
the fault that was immediately west of the previous earthquake.
saw the same types of patterns in Italy and China: Seismic activity
released along a network of faults, over time. But there's one area that
is currently of most concern to seismologists when it comes to
potential earthquake storms. Due to both the size and the geography of
California's San Andreas Fault—which is widely considered to be the most
overdue for some serious slippage—a single earthquake on that one fault
could actually start a chain-reaction of devastation up and down the
particular, in southern California, the Cucamonga Fault, which runs
west from Cajon Pass and along the southern base of the San Gabriel
Mountains, could rupture simultaneously with or soon after a major
earthquake along the San Andreas Fault. And that would lead to stress
changes along the Raymond Fault—which is at the western end of the
Cucamonga Fault—and from that to other faults in the Los Angeles region.
northern California, the Calaveras Fault splits off the main strand of
the San Andreas just south of San Juan Bautista. So a rupture of the
northern San Andreas Fault could lead to a rupture of the Calaveras—or
the Hayward or the Greenville or the San Gregorio Fault.
is to emphasize an important point: The exact sequence of future
ruptures, and hence major earthquakes, along the San Andreas and its
many adjacent faults cannot be predicted—which is why Jordan and others
issued probabilities in their reports. The series of quakes would not
disseminate out in a necessarily coherent direction.
But one thing
is certain: The last 100 years in California—which happen to correspond
to a period of rapid urban growth—have been a period of seismic calm.
That cannot continue.
The idea of stress transfer makes sense—of course
earthquakes could trigger other quakes since they, like, move the
earth—but these theories could change the way we can think about safety.
The idea that it likely won't be the San Andreas that will cause the
most damage, but a "local" fault in your own neighborhood, could help
create awareness and change development.
imagine something like a city-wide campaign to get to know your nearest
fault and learn how it might react. Plus, exploring the behavior of
earthquake storms could aid us in one possibly helpful way: It could
help cities see patterns and try to predict (somewhat) where and when
more earthquakes are coming.
entire story is fascinating and makes me want to pick up the book—not
to mention double the size of my earthquake preparedness kit. [Salon]