inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #76 of 126: Dan Flanery (sunspot) Tue 3 May 11 23:33
    
Seems to me much of the coastline in Oregon is pretty steep - there's
a beach with hills right behind it.  I guess there are some narrow
river valleys and such leading up to the shore, and I know I remember
some broader, flatter areas (Newport, Tillamook).  But I'd guess there
may not be a lot of tsunami deposits up thatway just because there
aren't a lot of places for stuff to be deposited near shore.

The area between Seattle and Vancouver has lots of low lying land,
though it's not exposed directly to the Pacific.
 
I'll bet landslides could cause tsunami in Puget Sound itself,
though...
 
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #77 of 126: Mark McDonough (mcdee) Wed 4 May 11 04:08
    
What got me thinking about people living on top of tsunami deposits
was reading a few years ago that much of Tacoma sits on top of quite
recent volcanic flow deposits - a lahar, I believe (very hot very
deadly mud flow).
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #78 of 126: Andrew Alden (alden) Wed 4 May 11 11:19
    
The tsunami deposits are documented in places like Willapa Bay, as sunspot
surmises.

I've been reading a paper about the tsunami of March 11. In some respects
tsunamis are actually another kind of earthquake, except that they occur in
liquid instead of solid settings. A release of energy excites waves, which
are well understood in terms of physics. The Japanese have many ocean-floor
observing stations and buoys that recorded the tsunami's passing, and it is
a simple matter to back-traject the waves to their origin, exactly like the
gunshot detectors in use in certain cities (also exactly like seismograph
networks in dtecting quakes). While the earthquake originated from a large
area about 500 kilometers long and 200 km wide, the tsunami came from a much
smaller patch where the seafloor was uplifted. That's important because
the greater part of the earthquake's energy was horizontal, which has no
effect on the water above the seafloor.

You may wonder whether another part of the crust was dropped down to
compensate for that uplift. It was Honshu and its offshore extension into
the Pacific that did that. The difficulties with the nuclear plants were
made worse because of that, making the shore more vulnerable to subsequent
tsunamis.
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #79 of 126: Andrew Alden (alden) Wed 4 May 11 13:53
    
I see that I misstated part of the paper. The tsunami was generated by the
whole rupture area, and the smaller area of extra uplift generated extra
tsunami waves on top of the main tsunami.

There is actually a category of earthquake called tsunami earthquakes, with
their own magnitude Mt (that's M-sub-t) based on the energy of the waves.
You don't see it often, because most earthquakes don't "concentrate" on
making tsunamis, but some do because of the particular blend of frequency
and spatial characteristics they exhibit.
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #80 of 126: Mark McDonough (mcdee) Wed 4 May 11 17:53
    
When my parents visited Hawaii 20 or 30 years ago, there was a tsunami
warning and you basically just had to head for the hills and wait to
see if it showed up (in this case it didn't).

I've noticed recently (meaning in the last few years) that tsunami
warnings tend to get canceled much more quickly - often, it seems,
within an hour of the earthquake.  In other words it seems like we know
pretty quickly whether a serious tsunami is going to happen.

Is this better monitoring, better software, more insights into how
they form, or a bit of all of the above?
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #81 of 126: Andrew Alden (alden) Wed 4 May 11 22:13
    
All of these, I think. I mentioned the Japanese and their networks of buoys
and seafloor instruments. More and more, these are monitored by satellite
telemetry for instant, coordinated display and processing. The faster a
quake can be characterized, the quicker a tsunami alert can be adjusted--and
I say "adjusted" because issuing an alert is automatic; deciding to call it
off is a human judgment. A useful guide to the different tsunami messages is
at <http://ptwc.weather.gov/ptwc/about_messages.php>; often people don't
take note of the difference between a "watch" and a "warning."

The cutting edge of this technology is real-time GPS data. When a large
network of GPS stations can report their exact positions once a second or
even faster, you have a dream machine for imaging earthquakes in real time.
That's important for characterizing the largest events, which are hard to
pin down quickly with current techniques. The Japanese has a prototype real-
time GPS network operating, but I haven't seen any reports yet on how it
did in March. One problem with the seismic network was that many stations
were wiped out or lost data, and that will probably remain the biggest
problem with the largest events.
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #82 of 126: Mark McDonough (mcdee) Thu 5 May 11 04:14
    
Hah - the "watch" and "warning" thing causes endless confusion in
tornado warnings as well.  I think there's a good case to be made for
adopting terms that make the difference a little clearer.
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #83 of 126: Mark McDonough (mcdee) Thu 5 May 11 04:18
    
Slowly waking up here...  

Speaking of warnings, I have read a couple of articles in the last
year or two about the idea of providing very near-term warnings of
serious earthquakes - taking advantage of the fact that electronic
messages can travel much faster than earthquake impulses can move
through the ground.

The idea would be to give people a few tens of seconds of advance
warning before the earthquake motions arrive - enough time to shut down
critical machines, for example, or perhaps even seek shelter.

Did this play any role in the recent Japanese quake?  Are there any
plans to put such a system into action in the US?
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #84 of 126: Andrew Alden (alden) Thu 5 May 11 11:22
    
The idea is old and obvious. To myknowledge the first time it was tried in a
modern way was after the 1989 Bay area earthquake. A small network of
sensors fed a computer at USGS headquarters in Menlo Park, which sent
aftershock alerts in real time over a microwave network. It gave rescuers in
Oakland a good 20 seconds of warning. Details of the system are at
<http://psn.quake.net/info/telemtry.txt>.

Mexico started an effective version a few years later, sending alerts to
Mexico City from the subduction zone off Guerrero.

The Japanese early warning system is the world's most advanced. I would love
it if people who were there could post their first-hand experiences with it.

Americans are far behind in this work, but prototype systems are in place in
California. Read more about it at <http://www.elarms.org/index.php>.

I can imagine as an American early-warning system emerges, we will go
through an arduous period of public education. I especially worry about the
mayhem that television stations could produce by doing the job poorly.
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #85 of 126: Mark McDonough (mcdee) Fri 6 May 11 06:04
    
Yes, as we were just saying, the confusion over "watches" and
"warnings" with respect to storms and tornadoes does not give one great
confidence.

We were talking a few days ago about the dramatic effect of the Lisbon
quake of 1755 had on history - influencing the Enlightenment and
bringing an end to Portugal's reign as a great power.

I was thinking about U.S. earthquakes and at least as far as I can
see, I'm ready to make the bold statement that no U.S. quake has a
serious effect on American history.

Am I wrong?
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #86 of 126: Andrew Alden (alden) Fri 6 May 11 09:45
    
So far so good, I think. We're a large country, unlike Portugal, and
earthquakes are a regional threat for us. No writer will be making an
alternate-history series in which, say, the 1906 earthquake didn't happen,
but the 1906 quake strongly influenced California history by allowing
Southern California to supplant Northern California as the center of power.
Of course, a Big One or two down there might turn things around.

On the other hand, we're a dumb and persistent species, a sort of crabgrass
species. Earthquakes are the equivalent of pesticide sprayed on one yard. We
seem to have no problem moving back into hazardous habitat, whether it's
Mississippi riverbanks, Malibu seacliffs or the slopes of Vesuvio. How to
regulate and/or mitigate our default behavior is a serious philosophical
problem. We were born to be wild, right?
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #87 of 126: Mark McDonough (mcdee) Fri 6 May 11 10:50
    
Hah, great analogy.

Re: the 1906 quake, the story I always heard when I was growing up was
"it wasn't so much the earthquake, but the fire."

Hasn't there been some relatively recent research that shows this was
sort of a cover story cooked up at the time to make SF look like a less
hazardous place?  In those days, especially, everyone could relate to
giant urban fires - then a common occurrence.

I've read that actually, most of the deaths and damage *were* from the
quake, although obviously there were some exceptions - like the modern
"fireproof" buildings along Market Street.

And as long as we're talking about earthquake myths - wooden buildings
are safer because they bend while others will break.  True or not
true, or "it depends."  I've read both sides of that argued with equal
passion.
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #88 of 126: Peter Meuleners (pjm) Fri 6 May 11 11:20
    
>>wooden buildings

I've read that doorways are not the haven they were once pumped up to
be because in a collapse they can fold and act like scissors.  I took
refuge in a doorway during the '89 quake.
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #89 of 126: Mark McDonough (mcdee) Fri 6 May 11 12:17
    
And that prompts another question.  I know many improvements have been
made to building design over the years, but have we yet seen what
happens when a city with a large number of truly tall buildings gets
hit with an 8+ earthquake?  I can't think of any such earthquake off
the top of my head.
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #90 of 126: Andrew Alden (alden) Fri 6 May 11 12:52
    
Well, there was Chile last year. I remember some comparisons in the press at
the time between casualties in the big cities versus the coastal towns.
We've kind of forgotten Chile already because it wasn't the huge catastrophe
it would have been a century ago.

I think we answered your question in 1906. San Francisco's downtown was full
of new, strongly engineered buildings designed by architects who were well
aware of earthquakes. The buildings performed well, in general, but the
infrastructure failed spectacularly when firefighters had no water. Only a
couple of fireboats with access to seawater saved the port from destruction.

The real question is, have we yet seen any city at all that is truly
resilient in the face of a major earthquake? I can't think of any such city
off the top of my head. Such a city would have to be designed de novo and
constructed and maintained with great integrity by a disciplined citizenry,
with the care and foresight we associate with major projects like suspension
bridges, the space program and nuclear power plants.

I think that realistically, we're stuck with suffering for the foreseeable
future. But we can always improve if we remember our lessons.
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #91 of 126: Andrew Alden (alden) Fri 6 May 11 13:13
    
Which reminds me of your other remark: "It wasn't so much the earthquake,
but the fire." There was a serious, concerted effort by San Francisco's
"movers and shakers" after 1906 to assure the world that "Frisco lives!" and
was still a good investment. And indeed, if capital had fled the city it
would have been a double disaster. Before television (and even radio), the
west coast was still a remote place. The stream of information out of the
city could be pretty well managed.

A big part of that campaign was assuring investors that the hazard was
slight and easily handled, so the fire was emphasized over the earthquake
from the start. When Fusakichi Omori, the world's foremost seismologist,
visited from Japan and declared that there would probably not be a
recurrence of the quake, it was interpreted as an all-clear signal. The
quake was a healthy thing that discharged all that nasty energy, probably
for centuries -- no, thousands of years! The fear of the unknown was the
worst barrier to reinvestment, so the quake had to explained away as quickly
as possible and the fire -- good old familiar fire, amenable to more
gumption and good sense -- was portrayed as the real villain.

I don't blame anyone for this, even if you could say it was just rich people
issuing propaganda to hoodwink their way back to prosperity. That's what we
do. Today things are more open, and earthquakes are better understood. No
one is making excuses in Japan, for instance, and investors have not
panicked.

My favorite book about the 1906 quake and its aftermath is Philip Fradkin's
"The Great Earthquake and Firestorms of 1906," reviewed at
<http://geology.about.com/od/bookreviews/fr/fradkin1906eq.htm>. The subtitle
is "How San Francisco Nearly Destroyed Itself."
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #92 of 126: Peter Meuleners (pjm) Fri 6 May 11 13:55
    
Didn't Kobe, Japan take a pretty big hit a few years ago?
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #93 of 126: Andrew Alden (alden) Fri 6 May 11 19:32
    
Yes it did, in 1995, and was rebuilt better than ever. As I said, investors
did not panic, although some 5000 people perished and all sorts of big,
impressive structures fell down.
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #94 of 126: Dan Flanery (sunspot) Fri 6 May 11 20:12
    
>I was thinking about U.S. earthquakes and at least as far
>as I can see, I'm ready to make the bold statement that no
>U.S. quake has a serious effect on American history.

I'm not sure if that's true.  I've read that the great New Madrid
quake had a huge impact on religion in the US, sparking a big revival
movement in the years following the quake.  End of the world and all
that bullshit.  From that beginning arose much of the fundie idiocy
plaguing the United States today.
 
I believe the 1906 quake also had enormous repercussions in the
financial markets.  From the Wikipedia article on the 1906 quake:

"The insurance payments heavily affected the international financial
system. Gold transfers from European insurance companies to
policyholders in San Francisco led to a rise in interest rates,
subsequently to a lack of available loans and finally to the
Knickerbocker Trust Company crisis of October 1907 which led to the
Panic of 1907"

The Panic of 1907 of course is the event that brought about the
creation of the Federal Reserve Bank...
 
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #95 of 126: Andrew Alden (alden) Fri 6 May 11 21:58
    
Those are two fun points. In arguing against them, I would say that the
United States has had waves of religious revival since the 1600s, and they
continue to this day. I can't see that the revivals of the 1810s have a
notable place in today's history books. It is interesting, though, that
Chief Tecumseh prophesied the event, which led directly to his ascent as a
great unifier of the Midwestern tribes in a military alliance against the US
government. I would argue that there was a more significant effect on our
history.

And as for the 1907 panic -- what we would today call a recession or
depression -- I would argue that a federal banking system was inevitable
given the continued instability of American capitalism.

It was not inevitable that Portugal would fall, earthquake or no.
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #96 of 126: Mark McDonough (mcdee) Sat 7 May 11 07:47
    
Haha - I was just about to say the same thing re: religious revivalism
- I'm not sure we needed an earthquake to get things going.  However,
I have read about some of the "end of the world" sermons preached in
response to it, so you may have a point.  I have a friend who majored
in religious studies - I'll put the question to him.
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #97 of 126: Mark McDonough (mcdee) Sat 7 May 11 12:23
    
Another fun earthquake myth - the old story that during an earthquake
cracks in the ground can open up and then close, trapping (according to
most of the stories) cows, sheep, and other assorted livestock.

I thought this was complete nonsense until I saw some of the cellphone
footage of soil liquefaction in Japan.  There was one sequence shot in
a park that was built entirely on fill that was a little scary.  This
was shot a long way from the epicenter, but yes, cracks did open up in
the ground, and you can imagine that if you were really close to the
epicenter of a major quake, that could actually happen.

The ubiquitous presence of high-quality cellphone cameras has really
changed the way we experience natural phenomena.  As recently as the
Indian ocean tsunami of a few years ago, mainly all we got to see is a
few pieces of footage from people crazy enough to hit "record" on their
video camera.  Now everyone with a cellphone in their pocket is a
filmmaker.
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #98 of 126: David Gans (tnf) Sat 7 May 11 12:42
    

When the Loma Prieta quake his (October 1989), I was sitting in my one-story
wooden home in the Oakland flatlands, talking to a friend who was sitting on
the second floor of her three-story wooden house at the base of the Berkeley
hills.  "DON'T HANG UP!" she ordered!  We sat together on the phone as our
respective huses creaked and shuddered for a very, very long time.

Neither house sustained any damage at all, not even a teacup falling off a
shelf.

Just a pair of data points.
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #99 of 126: Mark McDonough (mcdee) Sat 7 May 11 13:05
    
Interesting. 

I used to work in a (now gone) unreinforced masonry building in SF's
downtown.  I rode out one or two very small quakes there.  You don't
want to be in one of those.
  
inkwell.vue.406 : Andrew Alden on Earthquakes
permalink #100 of 126: Mark McDonough (mcdee) Sat 7 May 11 13:12
    
And sadly, my Reli Stu informant comes back with the answer "Don't
have a [censored] clue" re the relationship between the New Madrid
quakes and religious revivalism.

Of course, for all I know he studied cannon law in the Medieval
Church...
  

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