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RE: Misc Opinions

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Cliff (and Charlie):

So, I should have qualified my statement to be "sound engineering
judgement with some reasonable fudge factors" to be more accurate.  ;-)

But, also keep in mind that a 2,500 year earthquake does not mean that the
such a quake occurs every 2,500 years on the dot.  It means that on
average such an event occurs every 2,500 years.  So, it is quite possible
that such an event could occur tomorrow with a second occuring 10 years
latter and then another not occuring for about 5,000 years.

And, also keep in mind that smaller quakes can occur on a more frequent
"basis".  And considering that many buildings East of the Rockies were not
tradidtionally designed for seismic events (i.e. LOTS of unreinforced
masonry buildings) even a relatively minor quake could cause significant
damage and even loss of life in areas like the New Madrid zone.

Nels' recent post make some really good points.  Even in realitvely high
seismic regions like southern CA, many people don't "worry" too much about
seismic events until one happens.  Then everyone complains that "not
enough was done" yet THEY were the ones who did not want to spend the
money to make things more earthquake resistant.  All the "hubbub" lasts
for a year or so, then everyone goes back to their nice little safe
"world" where no quake could ever effect them and it becomes too expensive
to make things more earthquake resistant.  The biggest difference between
here (meaning East of the Rockies) and the West Coast is that they get
frequent wake up calls from mother nature while we here in the East can
"sleep" in ignorant bliss for longer period of time.

When you really think about it, it is kind of like terrorist threats.  We
in the U.S. sat around in lovely ignorant bliss until 9/11.  We had a few
wake up calls when the WTC was attacked in the 90s and a few other similar
events, but we went back to sleep.  This time we are staying awake a
little longer, but the reality is that at some point we will likely go
back to "sleep".  The point is that do you really think the threat was any
less real for the years prior to 9/11 than it is now?   Yet we certainly
all felt a lot more secure back then than we do now.

In the end, catastrophic events will happen.  They could be natural
(earthquakes, hurricanes, tornados, etc) or man-made (wars, terrorist
attacks, large scale accidents, etc).  The real question is do you sit
around in ignorant bliss or prepare.  And the coupled question is how much
preparedness is enough and how much it too much?  In otherwords, where is
the balance?

And in terms of seismic design, I agree with Charlie that the 2000 IBC
(and similar others) are a fairly good balance.  But, then that is just my
opinion, which is why the coupled question above is the tougher of the two
to answer because I am sure that there are those that would say that it is
not enough and other that would say that it is too much.

The thing to remember is that the last "record" of a major quake out of
the New Madrid zone has reports of church bells ringing in New England.
Now, if such a quake happen tomorrow, there could be some SERIOUS problems
to deal with in the aftermath.  Now, does something like the 2000 IBC
eliminate that problem?  Nope...cause most of the problem buildings are
already built and would likely not be retrofitted.  But, that does not
mean that we need to continue building new structures that are almost as
bad as older buildings rather than taking some prudent design measures to
make them more earthquake resistant.

So, the end result is that we (the U.S.) still have our heads in the sand
(if to a lesser degree) just like many "third world" countries when it
comes to setting seismic design as a high priority.  The biggest
difference is the one that Nels pointed out...since we don't (at least
most of us in the U.S.) have to worry about starving or freezing to death,
we can worry more about things like seismic resistance for our homes and
workplaces.  But, it is still something that tends to slip down the
priority scale below things like getting the new plamsa HD TV or new car,
etc.

Regards,

Scott
Ypsilanti, MI


On Wed, 31 Dec 2003, Carter, Charlie wrote:

> >Is it "sound engineering judgement" to design
> >buildings for the 2,500 year earthquake?
>
> Well, we don't really. First, we take two-thirds of it to get the MCE. Then,
> we throw in all these other fudge factors that dilute the actual earthquake
> for which we design.
>
> It's easy to get caught up in thinking we're overkilling design by using a
> "2,500-year earthquake". But the reality of what current seismic design
> requirements attempt to do is to have all buildings designed for a similar
> minimum probability against failure in a seismic event, regardless of where
> they are located.
>
> That makes sense to me.
>
> Charlie
>
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