<br><font size=2 face="sans-serif">Just to clarify, the quote </font><tt><font size=2>"the
2008 USGS hazard maps should not be substituted for the model building
code design maps nor should they be<br>
used with ASCE/SEI 41 or 31 for seismic rehabilitation or evaluation"</font></tt><font size=2 face="sans-serif">
is not from the Building Seismic Safety Council (BSSC) proposal for updated
seismic design criteria (http://www.bssconline.org/2nd09MOballot/Proj07props/ProposalSDPRG-1R4_07-07-08_Final.pdf),
but rather from the USGS webpage http://earthquake.usgs.gov/research/hazmaps/products_data/2008/disclaimer.php.
The full text from that webpage is pasted here:</font>
<br>
<br><font size=4 color=#004080 face="Verdana"><b>Important Note on Use
of New 2008 USGS Hazard Maps</b></font>
<p><font size=2 face="Verdana">Although it is anticipated that the new
2008 USGS <i>hazard</i> data will be the basis for the seismic <i>design</i>
maps in future editions of the NEHRP Recommended Provisions, the ASCE/SEI
7 Standard, and the International Building and Residential Codes, the values
on those seismic <i>design</i> maps are expected to be materially different
from the values on the 2008 <i>hazard</i> maps. More specifically, it is
anticipated that … </font>
<p><font size=2 face="sans-serif">1. </font><font size=2 face="Verdana">the
USGS hazard values will be amplified by factors that convert (approximately)
to spectral response accelerations in the maximum direction of ground motion,
</font>
<br><font size=2 face="sans-serif">2. </font><font size=2 face="Verdana">these
factored hazard values will be multiplied by “risk coefficients” that
adjust for a target <i>risk</i> (namely 1% probability of collapse in 50
years), and </font>
<br><font size=2 face="sans-serif">3. </font><font size=2 face="Verdana">these
factored and adjusted hazard values will be capped near known active faults
by so–called deterministic ground motions (like the USGS hazard values
were for the design maps in current editions of the model building codes).
</font>
<p><font size=2 face="Verdana"><b>Thus, 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.
</b></font>
<p><font size=2 face="Verdana">For more information, please click on the
following link to a recap of the </font><a href=http://bssconline.org/2008AnnualMeeting/08MeetingRecap.html target=_blank><font size=2 color=#0000e0 face="Verdana"><u>Building
Seismic Safety Council (BSSC) Seismic Design Procedures Reassessment Group
(SDPRG -- a.k.a., Project ‘07) Workshop </u></font></a><font size=2 face="Verdana">.</font>
<br>
<br><font size=2 face="sans-serif">This note was co-drafted by the USGS,
FEMA, and BSSC to remind engineers that while USGS <i>hazard maps</i> are
the basis for <i>design maps</i> in model building codes, hazard and design
maps are not one in the same (for example, due to the capping mentioned
in note #3 above). This was true of the 1996 and 2002 USGS hazard
maps and the building code design maps derived from them, and it continues
to be true (more so, in part due to notes #1-2 above) for the 2008 USGS
hazard maps and the design maps anticipated for the 2009 NEHRP Recommended
Provisions, 2010 ASCE 7 Standard, 2012 International Building and Residential
Codes, and next editions of ASCE/SEI 41 and 31.</font>
<br>
<br><font size=2 face="sans-serif">Please let me know if you have any questions/comments.</font>
<br>
<br><font size=2 face="sans-serif">----------------------------------------------------------------------------<br>
Nicolas Luco, PhD<br>
Research Structural Engineer<br>
U.S. Geological Survey<br>
<br>
Mailing Address:<br>
PO Box 25046, MS 966<br>
Denver, CO 80225<br>
<br>
Physical/Overnight Address:<br>
1711 Illinois Street, Room 426<br>
Golden, CO 80401<br>
<br>
Phone: (303)273-8683<br>
Fax: (303)273-8600<br>
----------------------------------------------------------------------------</font>
<br>
<br>
<br>
<br>
<table width=100%>
<tr valign=top>
<td width=40%><font size=1 face="sans-serif"><b>Seth Stein <seth@earth.northwestern.edu></b>
</font>
<br><font size=1 face="sans-serif">Sent by: ceus-earthquake-hazards-bounces@geohazards.usgs.gov</font>
<p><font size=1 face="sans-serif">01/14/2009 12:13 PM</font>
<table border>
<tr valign=top>
<td bgcolor=white>
<div align=center><font size=1 face="sans-serif">Please respond to<br>
"Central and Eastern U.S. Earthquake Hazards Listserve"
<ceus-earthquake-hazards@geohazards.usgs.gov></font></div></table>
<br>
<td width=59%>
<table width=100%>
<tr valign=top>
<td>
<div align=right><font size=1 face="sans-serif">To</font></div>
<td><font size=1 face="sans-serif">"ceus-earthquake-hazards@geohazards.usgs.gov"
<ceus-earthquake-hazards@geohazards.usgs.gov></font>
<tr valign=top>
<td>
<div align=right><font size=1 face="sans-serif">cc</font></div>
<td>
<tr valign=top>
<td>
<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td><font size=1 face="sans-serif">[CEUS-earthquake-hazards] Revised seismic
design criteria for New Madrid</font></table>
<br>
<table>
<tr valign=top>
<td>
<td></table>
<br></table>
<br>
<br>
<br><tt><font size=2>Readers may be interested in the latest proposal for
seismic building<br>
design criteria. In it "the 2008 USGS hazard maps should not be<br>
substituted for the model building code design maps nor should they be<br>
used with ASCE/SEI 41 or 31 for seismic rehabilitation or evaluation."<br>
<br>
Specifically, there are a set of scale (risk) factors to apply to the<br>
2008 USGS hazard maps to produce design maps: "Resulting risk<br>
coefficients are generally 0.85-1.15, but as low as 0.7 near New Madrid<br>
and Charleston".<br>
<br>
The USGS disclaimer<br>
<br>
http://earthquake.usgs.gov/research/hazmaps/products_data/2008/disclaimer.php
<br>
<br>
<br>
gives information about how the hazard maps are modified to<br>
produce design maps. For additional information, see<br>
<br>
http://bssconline.org/2008AnnualMeeting/080910--Luco1@BSSC_Annual_Mtg(Posted).pdf<br>
http://bssconline.org/2008AnnualMeeting/08MeetingRecap.html<br>
-- <br>
Seth Stein<br>
William Deering Professor<br>
Department of Earth and Planetary Sciences<br>
1850 Campus Drive<br>
Northwestern University, Evanston, IL 60208<br>
(847) 491-5265 FAX: (847) 491-8060 E-MAIL: seth@earth.northwestern.edu<br>
http://www.earth.northwestern.edu/people/seth<br>
<br>
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CEUS-Earthquake-Hazards@geohazards.usgs.gov<br>
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</font></tt>
<br>