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RE: Seismic Zones in Texas

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The IBC 2000 (which will soon be the only national building code in the
US)will be using the 1997 NEHRP as its basis.  There will be no more
"seismic zones".  The seismicity will be determined using seismic spectral
ordinates.  Check out the USGS site at

You will note in the left hand column under "Seismic Hazard" a listing for
Hazard by Zip Code and another listing for Hazard by Lat/Lon.  Use these to
determine the seismicity of the site and question.  Then follow along in the
1997 NEHRP to see what provisions apply.  

Harold Sprague
The Neenan Company

-----Original Message-----
From: Powers, Tony [mailto:tpowers(--nospam--at)]
Sent: Tuesday, January 05, 1999 10:18 AM
To: 'seaoc'
Subject: Seismic Zones in Texas

According to the Fig. 16-2 in the 1994 UBC (and I believe also the 1997
UBC), most of the state of Texas is in Seismic Zone 0.  I understand that
this is subject to change as the next code becomes more similar to ATC 32
(or we go to a national code), and that areas that are currently Zone 0 may
no longer be so in the future.  Does anyone out there know if/where I can
find some information on these changes?  A revised seismic Zone/acceleration
coefficient map would be ideal.

Thanks in advance.

Tony Powers
HDR Engineering, Inc.