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RE: Seismic Zones in Texas

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Dear Harold,

The USGS maps are not very accurate.  Even in there website they
indicate that the acceleration values are based on bedrock.  The
actual ground accelerations can be much higher.

Will there be any other kind of refinement short of structural
Engineers dealing with attenuation equations?

Thanx
Ken Tarlow



---Harold Sprague <harold.sprague(--nospam--at)neenan.com> wrote:
>
> 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
http://geohazards.cr.usgs.gov/eq/.
> 
> 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.  
> 
> Regards,
> Harold Sprague
> The Neenan Company
> harold.sprague(--nospam--at)neenan.com
> 
> 
> -----Original Message-----
> From: Powers, Tony [mailto:tpowers(--nospam--at)hdrinc.com]
> 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.
> 916-351-3837
> tpowers(--nospam--at)hdrinc.com
> 
> 
> 
> 
> 

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