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RE: Seismic Zones in Texas

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No, Ken, you are not getting old and afraid of change.  You are getting wiser 
in your older age.

What is happening is what Henry Petroski describes as the 30 year (or 35 
year) syndrome.  Since 30 to 35 years is the approximate working life of an 
individual, what he/she has learned *not* to do in that time, and the reasons 
for it, has not been adequately passed down to the younger members of the 
profession, they *don't* know what experience has shown to be inadequate.  
Therefore, we start having a series of failures every 30 - 35 years.

Compound this with educators that have had little or no practical experience 
who rely on computers that spit out answers in accordance with the 
instructions that *they* put into the computer and we are in for some *big* 

In the early 1960's it was a real chore to get masons to put reinforcing in 
masonry, at least here in Arizona.  ("All we need is a header every 5 courses 
and the wall is not going to go anywhere.")  Finally we were able to get 
masons to accept the need for reinforcing, however, the new masonry codes 
erode this requirement for seismic zone 2 locations by extrapolating tests 
that were intended only for small, single story, lightly loaded masonry 
construction to all masonry construction in seismic zone 2.

The USGS Seismic maps are not gospel.  Depending on how the head of the USGS 
seismic branch wants to have the maps look will depend on what we see.  
Algermissen's first map (1971), based on historical seismicity, was quite a 
bit different than his second map (ca. 1985), based strictly on probability 
(and politically modified), which is quite a bit different than Arthur 
Frankel's map (ca.1990's), which is based on a combination of probability and 
historical seismicity, which is quite a bit different from his map that 
doesn't have the accelerations divided by 4.  Have you seen the USGS map that 
shows California accelerations of 3.9g?  I would venture to say that very few 
people have.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Ken Tarlow wrote:

. > Is anyone else thinking this will be a disaster? or am I just getting
. > old and am afraid of change.