[CEUS-earthquake-hazards] The balance

[Seth Stein]

I think your point is very well taken. I've recently seen a case
where reducing costs is said to have made a mitigation measure cost
effective. There's a recent study (you may know it) by the National 
Institute of Standards and Technology "Benefit-Cost Analysis of 
Residential Fire Sprinkler Systems"

http://fire.nist.gov/bfrlpubs/build07/art025.html

The study argues that although analysis in 1984 found that residential 
sprinkler systems were not cost-effective,
improvements in their performance and cost now make them
cost-effective.

I don't know enough about the specifics to say more,
but it looks like the kind of objective outside study that would
be useful in considering various seismic mitigation strategies.
My recommendation (for the central U.S.) has been to do this via
the National Academy of Sciences /National Academy of Engineering
study process

http://www.nationalacademies.org/studyprocess/index.html

which is likely to produce sensible results that will be generally 
accepted.This is the approach being taken for hurricane protection 
policy for New Orleans.

http://www8.nationalacademies.org/cp/projectview.aspx?key=335
New Orleans Regional Hurricane Protection Projects


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Seth Stein
William Deering Professor
Department of Earth and Planetary Sciences
1850 Campus Drive
Northwestern University, Evanston, IL 60208
(847) 491-5265 FAX: (847) 491-8060 E-MAIL: seth at earth.northwestern.edu
http://www.earth.northwestern.edu/people/seth


Goldfarb, Lawrence wrote:
> To All:
>  
> I have enjoyed this discussion immensely.  I believe one of our main 
> challenges here is to make sure the policy makers are educated enough to 
> make these very important and difficult decisions and are not weighing 
> politics ahead of the state of the practice. It is very easy to do and 
> happens all too often.
>  
> Perhaps we are attacking this issue at the wrong level.  Rather than 
> lowering seismic buildign codes, we may serve the public better by 
> working from that point forward in the retrofit process.  We can work 
> smarter and have the local engineering community perform site specific 
> response analyses for these facilities. I recall having this same issue 
> come up in the Bay Area in the early to mid 1980's (prior to Mexico 
> City, Loma Prieta, Northridge, Kobe, etc.).  Harry Seed had done great 
> work to demonstrate the effects of the geotechnical conditions on ground 
> motion from various causative events.  I truly learned a lot from him.  
> We realized that the site class is used to try to account for this, but 
> numerous studies indicate that even slight changes in the shear wave 
> velocity of soils can have a marked change on ground motion.  Obviously 
> the code is not designed to, nor can it account for, these changes. 
>  
> A 110 billion dollar number is a lot of money.  If a small sprinkle of 
> that was used to perform site specific response analyses combined with 
> modern structural analysis and development of  innovative construction 
> retrofit techniques, I believe the public will be better served.  In 
> engineering practice, that is how we have served our clients and it has 
> given then the biggest bang for the buck. Having been involved on 60 
> retrofit bridge projects for Caltrans in the early 1990's, (also with a 
> very limited budget, given the shear number of structures and few state 
> dollars)  we found that by performing more sophisticated 
> analyses, the retrofits could range from simple cable restrainers to 
> brand new foundations and bent structures.   I believe this approach 
> to be much better  then spending our time manipulating the probable 
> magnitude of the events to meet our budget constraints. 
> 
> CDM
> 
> 
> *Lawrence P. Goldfarb, P.E.*
> Sr. Geotechnical Engineer , Group Leader
> 
> 3130 Fairview Park Drive
> Falls Church, VA 22042-4517
> 
>azards.cr.usgs.gov/mailman/listinfo/ceus-earthquake-hazards
> 


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