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<DIV dir=ltr align=left><SPAN class=400541814-23012009><FONT face=Arial
color=#0000ff size=2>Nicolas,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=400541814-23012009><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=400541814-23012009><FONT face=Arial
color=#0000ff size=2>Thanks for sharing what's going on with the USGS
maps. I'm a little confused. Sounds like the "real risk" is lower
than previously expected so some other changes are being made to prop the map's
design ground motions back up to a level that "feels good". For
example, what is the justfication for changing the hazard basis of the map from
2% in 50-years to 1% in 50 years. Why not 5 to 10% in 50-years
instead? We have a good calibration in California for what has worked in
the past with reasonable success. Why are we not using this as a hard
calibration point for risk and then sticking with a risk consistent application
of that calibration across the country? It still seems like the map
is wondering around in the abyss of relativism and politics and
someone needs to calibrate it to an "absolute" condition that has worked by
experience. Is my description fair?</FONT></SPAN></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=400541814-23012009>I also have a
question regarding directionality of ground motion. If the worst case
horizontal ground motion will be used for the design map, then how will the
probability of that ground motion being aligned with the worst-cast orientation
of any given building be handled? It would seem that if the maps change in
this regard, then a probability adjustment factor of less than one is needed to
avoid a systematic conservative bias in the design provisions. This same
concern is addressed by a wind load directionality factor of 0.85.
But, maybe the bias is intended for seismic?</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=400541814-23012009></SPAN></FONT><FONT
face=Arial size=2><SPAN class=400541814-23012009></SPAN></FONT><FONT face=Arial
size=2></FONT> </DIV>
<DIV><SPAN class=400541814-23012009><FONT face=Arial
size=2>Thanks,</FONT></SPAN></DIV>
<DIV><SPAN class=400541814-23012009><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=400541814-23012009><FONT face=Arial
size=2>Jay</FONT></SPAN></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>ARES Consulting</FONT></DIV>
<DIV align=left><FONT face=Arial size=2>5095 Sudley Rd</FONT></DIV>
<DIV align=left><FONT face=Arial size=2>West River, MD 20778</FONT></DIV>
<DIV align=left><FONT face=Arial size=2>410-867-9617</FONT></DIV>
<DIV align=left><FONT face=Arial size=2>410-867-9618 fax</FONT></DIV>
<DIV> </DIV><BR>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B>
ceus-earthquake-hazards-bounces@geohazards.usgs.gov
[mailto:ceus-earthquake-hazards-bounces@geohazards.usgs.gov] <B>On Behalf Of
</B>Nicolas Luco<BR><B>Sent:</B> Thursday, January 22, 2009 6:59
PM<BR><B>To:</B> Central and Eastern U.S. Earthquake Hazards
Listserve<BR><B>Subject:</B> Re: [CEUS-earthquake-hazards] Revised seismic
design criteria forNew Madrid<BR></FONT><BR></DIV>
<DIV></DIV><BR><FONT face=sans-serif size=2>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.</FONT> <BR><BR><FONT face=sans-serif
size=2>Again, please let me know if you have any questions/comments
</FONT><BR><BR><FONT face=sans-serif
size=2>----------------------------------------------------------------------------<BR>Nicolas
Luco<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>
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<TD width="40%"><FONT face=sans-serif size=1><B>Seth Stein
<seth@earth.northwestern.edu></B> </FONT><BR><FONT face=sans-serif
size=1>Sent by: ceus-earthquake-hazards-bounces@geohazards.usgs.gov</FONT>
<P><FONT face=sans-serif size=1>01/14/2009 12:13 PM</FONT>
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<DIV align=center><FONT face=sans-serif size=1>Please respond
to<BR>"Central and Eastern U.S. Earthquake Hazards Listserve"
<ceus-earthquake-hazards@geohazards.usgs.gov></FONT></DIV></TR></TBODY></TABLE><BR></P>
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<DIV align=right><FONT face=sans-serif size=1>To</FONT></DIV>
<TD><FONT face=sans-serif
size=1>"ceus-earthquake-hazards@geohazards.usgs.gov"
<ceus-earthquake-hazards@geohazards.usgs.gov></FONT>
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<TD>
<DIV align=right><FONT face=sans-serif size=1>cc</FONT></DIV>
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<DIV align=right><FONT face=sans-serif size=1>Subject</FONT></DIV>
<TD><FONT face=sans-serif size=1>[CEUS-earthquake-hazards] Revised
seismic design criteria for New
Madrid</FONT></TR></TBODY></TABLE><BR>
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<TD></TR></TBODY></TABLE><BR></TR></TBODY></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>_______________________________________________<BR>CEUS-Earthquake-Hazards
mailing
list<BR>CEUS-Earthquake-Hazards@geohazards.usgs.gov<BR>https://geohazards.usgs.gov/mailman/listinfo/ceus-earthquake-hazards<BR></FONT></TT><BR></BODY></HTML>