[CEUS-earthquake-hazards] Revised seismic design criteria for New Madrid

[Nicolas Luco]

Another clarification:  In addition to the risk coefficients mentioned 
below, there are "maximum direction" amplification factors of 1.1 and 1.3 
for, respectively, 0.2- and 1.0-second spectral acceleration that are 
applied to the 2008 USGS hazard maps in deriving updated design maps for 
building codes.  Furthermore, the 2008 hazard maps themselves are 
different than the 2002 (and 1996) hazard maps, as are the corresponding 
deterministic "caps" that are applied to the respective hazard maps. Thus, 
the updated design maps based on the 2008 hazard maps are not simply lower 
than previous design maps by a factor of 0.7 near New Madrid and 
Charleston.  In fact, in some cases the new design map values may be about 
the same as the previous ones.

Again, please let me know if you have any questions/comments 

----------------------------------------------------------------------------
Nicolas Luco
Research Structural Engineer
U.S. Geological Survey

Mailing Address:
PO Box 25046, MS 966
Denver, CO 80225

Physical/Overnight Address:
1711 Illinois Street, Room 426
Golden, CO 80401

Phone: (303)273-8683
Fax: (303)273-8600
----------------------------------------------------------------------------




Seth Stein <seth at earth.northwestern.edu> 
Sent by: ceus-earthquake-hazards-bounces at geohazards.usgs.gov
01/14/2009 12:13 PM
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Subject
[CEUS-earthquake-hazards] Revised seismic design criteria for New Madrid






Readers may be interested in the latest proposal for seismic building
design criteria. In it "the 2008 USGS hazard maps should not be
substituted for the model building code design maps nor should they be
used with ASCE/SEI 41 or 31 for seismic rehabilitation or evaluation."

Specifically, there are a set of scale (risk) factors to apply to the
2008 USGS hazard maps to produce design maps: "Resulting risk
coefficients are generally 0.85-1.15, but as low as 0.7 near New Madrid
and Charleston".

The USGS disclaimer

http://earthquake.usgs.gov/research/hazmaps/products_data/2008/disclaimer.php 



gives  information about how the hazard maps are modified to
produce design maps. For additional information, see

http://bssconline.org/2008AnnualMeeting/080910--Luco1@BSSC_Annual_Mtg(Posted).pdf

http://bssconline.org/2008AnnualMeeting/08MeetingRecap.html
-- 
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

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