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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>I would like to offer a point of support to
the discussion, while at the same time a word of caution. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The discussion surrounding the hazard is
important and needs to be addressed. From my perspective these issues are
fundamentally research based and as such should be debated within the research
community. This list serve, while sponsored by USGS and designed to allow
such discussion among professionals, it is not exclusive to the scientific community,
meaning any and everyone who wants to join can, i.e. elected officials, media, emergency
management, business owners, etc., most of which have an interest in the hazard
in the central US but no seismic research/engineering background. This mix
can be unintentionally problematic with discussions like these currently taking
place, because it breaks from what I would consider the proper forum to be in resolving
such an issue and adds to the overall confusion. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>There is a “time and place for
everything” as the saying goes and I don’t feel this list serve is
the place for this discussion. The topic is to technical and the end
results of the debate, whichever way they may go, need to be decided off line
and within the scientific community. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><st1:PersonName w:st="on"><font size=2 color=navy
face=Arial><span style='font-size:10.0pt;font-family:Arial;color:navy'>Jim
Wilkinson</span></font></st1:PersonName><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Executive Director<o:p></o:p></span></font></p>
<p class=MsoNormal><st1:place w:st="on"><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>Central United States</span></font></st1:place><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'> Earthquake Consortium<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'> ceus-earthquake-hazards-bounces@geohazards.usgs.gov
[mailto:ceus-earthquake-hazards-bounces@geohazards.usgs.gov] <b><span
style='font-weight:bold'>On Behalf Of </span></b>Emitt C Witt<br>
<b><span style='font-weight:bold'>Sent:</span></b> Friday, February 15, 2008
12:16 PM<br>
<b><span style='font-weight:bold'>To:</span></b> Allen Jones<br>
<b><span style='font-weight:bold'>Cc:</span></b>
ceus-earthquake-hazards@geohazards.usgs.gov; ceus-earthquake-hazards-bounces@geohazards.usgs.gov<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re:
[CEUS-earthquake-hazards] reply to Joe Tomasello; buildings codes and
earthquake hazard</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><br>
</span></font><font size=2 face=sans-serif><span style='font-size:10.0pt;
font-family:sans-serif'>I concur with Allen. Unless the discussion gets personal,
and it has not, I'd like to see it stay open to everyone on this list serve.
Not being a seismologist or a practicing structural engineer, I have found the
discussion interesting and educational.</span></font> <br>
<br>
<font size=2 face=sans-serif><span style='font-size:10.0pt;font-family:sans-serif'>Emitt</span></font>
<br>
<font size=2 face=sans-serif><span style='font-size:10.0pt;font-family:sans-serif'>________________________________________<br>
Emitt C. Witt III, P.H.<br>
Director, Mid-Continent Geographic <st1:place w:st="on"><st1:PlaceName w:st="on">Science</st1:PlaceName>
<st1:PlaceType w:st="on">Center</st1:PlaceType></st1:place><br>
<st1:Street w:st="on"><st1:address w:st="on">1400 Independence Road</st1:address></st1:Street><br>
<st1:place w:st="on"><st1:City w:st="on">Rolla</st1:City>, <st1:State w:st="on">Missouri</st1:State>
<st1:PostalCode w:st="on">65401</st1:PostalCode></st1:place><br>
573-308-3679<br>
573-308-3794 FAX<br>
http://mcmcweb.er.usgs.gov/mcgsc<br>
</span></font><br>
<br>
<o:p></o:p></p>
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<p class=MsoNormal><b><font size=1 face=sans-serif><span style='font-size:
7.5pt;font-family:sans-serif;font-weight:bold'>Allen Jones
<jonesal@myuw.net></span></font></b><font size=1 face=sans-serif><span
style='font-size:7.5pt;font-family:sans-serif'> </span></font><br>
<font size=1 face=sans-serif><span style='font-size:7.5pt;font-family:sans-serif'>Sent
by: ceus-earthquake-hazards-bounces@geohazards.usgs.gov</span></font> <o:p></o:p></p>
<p><font size=1 face=sans-serif><span style='font-size:7.5pt;font-family:
sans-serif'>02/15/2008 11:14 AM</span></font> <o:p></o:p></p>
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<p class=MsoNormal align=right style='text-align:right'><font size=1
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<p class=MsoNormal><font size=1 face=sans-serif><span style='font-size:
7.5pt;font-family:sans-serif'>"ceus-earthquake-hazards@geohazards.usgs.gov"
<ceus-earthquake-hazards@geohazards.usgs.gov></span></font> <o:p></o:p></p>
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<p class=MsoNormal align=right style='text-align:right'><font size=1
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<p class=MsoNormal align=right style='text-align:right'><font size=1
face=sans-serif><span style='font-size:7.5pt;font-family:sans-serif'>Subject</span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=1 face=sans-serif><span style='font-size:
7.5pt;font-family:sans-serif'>Re: [CEUS-earthquake-hazards] reply to Joe
Tomasello; buildings codes and earthquake hazard</span></font><o:p></o:p></p>
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<br>
<br>
</span></font><tt><font size=2 face="Courier New"><span style='font-size:10.0pt'>Speaking
for myself, I find these discussions very interesting and informative. I
find think this sort of intellectual debate healthy and provides a perspective
missing from publications. I encourage you to keep the discussion public
and appreciate everyone's efforts in taking the time to respond.</span></font></tt><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New"'><br>
<br>
<tt><font face="Courier New">Allen Jones</font></tt><br>
<tt><font face="Courier New">________________________</font></tt><br>
<tt><font face="Courier New">Allen Jones, PE, PhD</font></tt><br>
<st1:place w:st="on"><st1:PlaceName w:st="on"><tt><font face="Courier New">South
Dakota</font></tt></st1:PlaceName><tt><font face="Courier New"> <st1:PlaceType
w:st="on">State</st1:PlaceType> <st1:PlaceType w:st="on">University</st1:PlaceType></font></tt></st1:place><br>
<tt><font face="Courier New">Department of Civil Engineering</font></tt><br>
<tt><font face="Courier New">CEH 148, <st1:address w:st="on"><st1:Street w:st="on">Box</st1:Street>
2219</st1:address></font></tt><br>
<st1:place w:st="on"><st1:City w:st="on"><tt><font face="Courier New">Brookings</font></tt></st1:City><tt><font
face="Courier New">, <st1:State w:st="on">SD</st1:State> <st1:PostalCode
w:st="on">57006</st1:PostalCode></font></tt></st1:place><br>
<br>
<tt><font face="Courier New">Direct: 605-688-6467</font></tt><br>
<tt><font face="Courier New">Fax: 605-688-6476</font></tt><br>
<br>
<tt><font face="Courier New">On Fri, 15 Feb 2008, Arthur D Frankel wrote:</font></tt><br>
<br>
<tt><font face="Courier New">> Zhenming,</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> I am sure many people on the bulletin
board are getting tired of these</font></tt><br>
<tt><font face="Courier New">> exchanges.</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> I presented similar comparisons at the
Applied Technology Council</font></tt><br>
<tt><font face="Courier New">> workshop in <st1:City w:st="on"><st1:place
w:st="on">Memphis</st1:place></st1:City> in March 2005. As I recall, you
and Joe Tomasello</font></tt><br>
<tt><font face="Courier New">> were in attendance. So I think you
have seen these comparisons.</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> Of course, I don't see any contradiction in
what I've said. I think it</font></tt><br>
<tt><font face="Courier New">> is reasonable to compare code values with the
expected ground motions from</font></tt><br>
<tt><font face="Courier New">> the next 1811-12 type earthquake and with
ground motions estimated for the</font></tt><br>
<tt><font face="Courier New">> 1811-12 earthquakes using intensity
observations.</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> I think further discussion between us
on these issues should be made off</font></tt><br>
<tt><font face="Courier New">> of the bulletin board.</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> -Art</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> Art Frankel</font></tt><br>
<tt><font face="Courier New">> <st1:country-region w:st="on"><st1:place
w:st="on">U.S.</st1:place></st1:country-region> Geological Survey</font></tt><br>
<tt><font face="Courier New">> MS 966, Box 25046</font></tt><br>
<tt><font face="Courier New">> DFC</font></tt><br>
<tt><font face="Courier New">> <st1:place w:st="on"><st1:City w:st="on">Denver</st1:City>,
<st1:State w:st="on">CO</st1:State> <st1:PostalCode w:st="on">80225</st1:PostalCode></st1:place></font></tt><br>
<tt><font face="Courier New">> phone: 303-273-8556</font></tt><br>
<tt><font face="Courier New">> fax: 303-273-8600</font></tt><br>
<tt><font face="Courier New">> email: <st1:PersonName w:st="on">afrankel@usgs.gov</st1:PersonName></font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> "Wang, Zhenming"
<zmwang@email.uky.edu></font></tt><br>
<tt><font face="Courier New">> 02/15/2008 08:35 AM</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> To</font></tt><br>
<tt><font face="Courier New">> Arthur D Frankel <<st1:PersonName w:st="on">afrankel@usgs.gov</st1:PersonName>></font></tt><br>
<tt><font face="Courier New">> cc</font></tt><br>
<tt><font face="Courier New">> James Cobb <cobb@uky.edu>,
"Keifer, John D" <kiefer@email.uky.edu>,</font></tt><br>
<tt><font face="Courier New">>
"ceus-earthquake-hazards@geohazards.usgs.gov"</font></tt><br>
<tt><font face="Courier New">> <ceus-earthquake-hazards@geohazards.usgs.gov></font></tt><br>
<tt><font face="Courier New">> Subject</font></tt><br>
<tt><font face="Courier New">> RE: [CEUS-earthquake-hazards] reply to Joe
Tomasello; buildings codes</font></tt><br>
<tt><font face="Courier New">> and earthquake hazard</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> Art,</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> This is the first time we see these
comparisons:</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> ?When I talk to code committees and other
groups, I compare the relative</font></tt><br>
<tt><font face="Courier New">> level of protection that designing to
different probability levels of</font></tt><br>
<tt><font face="Courier New">> ground shaking will provide to buildings.
This can be assessed by</font></tt><br>
<tt><font face="Courier New">> comparing the ground-motion values for the
probability levels in the</font></tt><br>
<tt><font face="Courier New">> building codes to the median ground motions
expected when the next 1811-12</font></tt><br>
<tt><font face="Courier New">> type New Madrid earthquake occurs and by
comparing code values to</font></tt><br>
<tt><font face="Courier New">> intensities observed in the <st1:City w:st="on"><st1:place
w:st="on">Memphis</st1:place></st1:City> area from the 1811-12 earthquakes.?</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> The selected design ground motion should be
consistent with the scientific</font></tt><br>
<tt><font face="Courier New">> facts. However, these comparisons seem to be
contradictory to your early</font></tt><br>
<tt><font face="Courier New">> statements:</font></tt><br>
<tt><font face="Courier New">> 1. ?In fact, we release
seismic hazard curves (a range of ground</font></tt><br>
<tt><font face="Courier New">> motion, from 0.0 to 10g or larger) for a grid
of sites across the nation,</font></tt><br>
<tt><font face="Courier New">> so that users can calculate the ground
motions at any probability level</font></tt><br>
<tt><font face="Courier New">> they choose.? ?It should also be reiterated
that the national seismic</font></tt><br>
<tt><font face="Courier New">> hazard maps are based on the average hazard
curves from a variety of input</font></tt><br>
<tt><font face="Courier New">> models and attenuation relations; they are
not worst-case maps.?</font></tt><br>
<tt><font face="Courier New">> 2. ?It is not correct to
compare the intensity observations from</font></tt><br>
<tt><font face="Courier New">> 1811-1812 with the probabilistic hazard maps
that also include the hazard</font></tt><br>
<tt><font face="Courier New">> from earthquakes closer to St. Louis.?</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> Thanks.</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> Zhenming</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> From:
ceus-earthquake-hazards-bounces@geohazards.usgs.gov</font></tt><br>
<tt><font face="Courier New">>
[mailto:ceus-earthquake-hazards-bounces@geohazards.usgs.gov] On Behalf Of</font></tt><br>
<tt><font face="Courier New">> Arthur D Frankel</font></tt><br>
<tt><font face="Courier New">> Sent: Thursday, February 14, 2008 3:35 PM</font></tt><br>
<tt><font face="Courier New">> To: ceus-earthquake-hazards@geohazards.usgs.gov</font></tt><br>
<tt><font face="Courier New">> Subject: [CEUS-earthquake-hazards] reply to
Joe Tomasello; buildings codes</font></tt><br>
<tt><font face="Courier New">> and earthquake hazard</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> Joe,</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> The USGS policy is to support the process of
the Building Seismic Safety</font></tt><br>
<tt><font face="Courier New">> Council (BSSC) establishing probability
levels and design procedures for</font></tt><br>
<tt><font face="Courier New">> the national model building codes, such as
the <st1:place w:st="on"><st1:PlaceName w:st="on">International</st1:PlaceName>
<st1:PlaceType w:st="on">Building</st1:PlaceType></st1:place></font></tt><br>
<tt><font face="Courier New">> Code. The BSSC membership consists of a
large group of engineers and</font></tt><br>
<tt><font face="Courier New">> stakeholders. The BSSC is a council of the
National Institute of Building</font></tt><br>
<tt><font face="Courier New">> Sciences. The code development process of the
BSSC is funded by FEMA. The</font></tt><br>
<tt><font face="Courier New">> design procedures are published in the NEHRP
Recommended Provisions for</font></tt><br>
<tt><font face="Courier New">> the Development of Seismic Regulations for
New Buildings, which is written</font></tt><br>
<tt><font face="Courier New">> by the BSSC/NIBS and published by FEMA.</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> I think a key responsibility of the USGS is
to provide the best scientific</font></tt><br>
<tt><font face="Courier New">> information to decision makers. Part of
this scientific information is</font></tt><br>
<tt><font face="Courier New">> assessment of the ground motions from the
1811-12 earthquakes and</font></tt><br>
<tt><font face="Courier New">> estimation of the ground motions for the next
1811-12 type earthquake.</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> When I talk to code committees and other
groups, I compare the relative</font></tt><br>
<tt><font face="Courier New">> level of protection that designing to
different probability levels of</font></tt><br>
<tt><font face="Courier New">> ground shaking will provide to buildings.
This can be assessed by</font></tt><br>
<tt><font face="Courier New">> comparing the ground-motion values for the
probability levels in the</font></tt><br>
<tt><font face="Courier New">> building codes to the median ground motions
expected when the next 1811-12</font></tt><br>
<tt><font face="Courier New">> type New Madrid earthquake occurs and by
comparing code values to</font></tt><br>
<tt><font face="Courier New">> intensities observed in the <st1:City w:st="on"><st1:place
w:st="on">Memphis</st1:place></st1:City> area from the 1811-12 earthquakes.</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> For example, the value of ground motions
around 1 Hz with a 10%</font></tt><br>
<tt><font face="Courier New">> probability of exceedance in 50 years
(10%/50) is substantially lower than</font></tt><br>
<tt><font face="Courier New">> the median 1 Hz ground motion expected for
the next 1811-12 type</font></tt><br>
<tt><font face="Courier New">> earthquake. The new <st1:City w:st="on"><st1:place
w:st="on">Memphis</st1:place></st1:City> code adopted in 2006 uses the 10%/50
year</font></tt><br>
<tt><font face="Courier New">> ground motions from the 1996 vintage of the
national maps (the 2002 maps</font></tt><br>
<tt><font face="Courier New">> are higher). Here I am considering 1 Hz
spectral accelerations (<st1:country-region w:st="on"><st1:place w:st="on">S.A.</st1:place></st1:country-region>),</font></tt><br>
<tt><font face="Courier New">> which are used for the design of buildings
with about 10 stories. For a</font></tt><br>
<tt><font face="Courier New">> site in <st1:City w:st="on"><st1:place w:st="on">Memphis</st1:place></st1:City>
(35.15 N; 90.05 W), the 10%/50 value of 1 Hz spectral</font></tt><br>
<tt><font face="Courier New">> acceleration is 0.16g (from the 1996 maps and
using an amplification</font></tt><br>
<tt><font face="Courier New">> factor of 2.4 for class D stiff-soil site
relative to firm-rock site from</font></tt><br>
<tt><font face="Courier New">> the NEHRP amplification factors). This
is much lower than the median 1 Hz</font></tt><br>
<tt><font face="Courier New">> <st1:country-region w:st="on">S.A.</st1:country-region>
of 0.36g expected in <st1:City w:st="on"><st1:place w:st="on">Memphis</st1:place></st1:City>
from a scenario earthquake with moment</font></tt><br>
<tt><font face="Courier New">> magnitude 7.7 located on the portion of the
current New Madrid seismicity</font></tt><br>
<tt><font face="Courier New">> trend northwest of <st1:City w:st="on"><st1:place
w:st="on">Memphis</st1:place></st1:City> (using the stiff-soil amplification
factor from</font></tt><br>
<tt><font face="Courier New">> the NEHRP factors). This calculation of the
expected spectral acceleration</font></tt><br>
<tt><font face="Courier New">> is based on the average of the five
attenuation relations used in the 2002</font></tt><br>
<tt><font face="Courier New">> national maps. If the next large New
Madrid earthquake was a moment</font></tt><br>
<tt><font face="Courier New">> magnitude 7.4, the calculated median 1 Hz
S.A. at <st1:City w:st="on"><st1:place w:st="on">Memphis</st1:place></st1:City>
would be 0.29g</font></tt><br>
<tt><font face="Courier New">> for a stiff-soil site, still much higher than
the 10%/50 value (0.16g)</font></tt><br>
<tt><font face="Courier New">> from the 1996 maps.</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> The 10%/50 values for 1 Hz S.A. from the 2002
hazard maps would still be</font></tt><br>
<tt><font face="Courier New">> significantly lower than the scenario ground
motions. For 5 Hz S.A., the</font></tt><br>
<tt><font face="Courier New">> expected values of the median ground motions
for a M7.7 earthquake are</font></tt><br>
<tt><font face="Courier New">> more sensitive to assumptions on the
nonlinearity and attenuation of</font></tt><br>
<tt><font face="Courier New">> sediments in the Mississippi Embayment.</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> The International Building Code (IBC) uses
spectral accelerations that are</font></tt><br>
<tt><font face="Courier New">> 2/3 times the values with a 2% probability of
exceedance in 50 years for</font></tt><br>
<tt><font face="Courier New">> most of the nation (there are some areas
where IBC uses the median</font></tt><br>
<tt><font face="Courier New">> deterministic ground motions, depending on
the level of the probabilistic</font></tt><br>
<tt><font face="Courier New">> motions). For 1 Hz S.A., the 2006 IBC
specifies a value of 0.42g for</font></tt><br>
<tt><font face="Courier New">> <st1:City w:st="on"><st1:place w:st="on">Memphis</st1:place></st1:City>
(stiff-soil site). This is similar to the median value of 0.36g</font></tt><br>
<tt><font face="Courier New">> expected for a M7.7 earthquake (see above).</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> In my presentations, I also compare the code
values to the ground motions</font></tt><br>
<tt><font face="Courier New">> estimated from intensity reports in the <st1:City
w:st="on"><st1:place w:st="on">Memphis</st1:place></st1:City> area from past</font></tt><br>
<tt><font face="Courier New">> earthquakes. Here I use peak ground
accelerations (PGA) rather than</font></tt><br>
<tt><font face="Courier New">> spectral accelerations, because intensities
are generally correlated in</font></tt><br>
<tt><font face="Courier New">> the literature with PGA?s or peak ground
velocities.</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> Intensities in the <st1:City w:st="on"><st1:place
w:st="on">Memphis</st1:place></st1:City> area during the 1811-12 earthquakes
have been</font></tt><br>
<tt><font face="Courier New">> assigned as intensity VIII by Hough et al.
(2000) and as intensity X by</font></tt><br>
<tt><font face="Courier New">> <st1:City w:st="on"><st1:place w:st="on">Johnston</st1:place></st1:City>
(1996), depending on their interpretation of earthquake effects.</font></tt><br>
<tt><font face="Courier New">> Intensity VIII corresponds to a peak ground
acceleration between about</font></tt><br>
<tt><font face="Courier New">> 0.34 and 0.65g, based on the work David Wald
did for Shakemap. This range</font></tt><br>
<tt><font face="Courier New">> is consistent with the calculated median PGA
at <st1:City w:st="on"><st1:place w:st="on">Memphis</st1:place></st1:City> of
0.39g for a</font></tt><br>
<tt><font face="Courier New">> M7.7 earthquake determined from the average
of 5 attenuation relations</font></tt><br>
<tt><font face="Courier New">> used in the 2002 hazard maps (using the NEHRP
amplification factors). The</font></tt><br>
<tt><font face="Courier New">> calculated PGA for a M7.4 earthquake is
0.32g, close to the range of the</font></tt><br>
<tt><font face="Courier New">> PGA?s estimated for intensity VIII.</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> The new <st1:City w:st="on"><st1:place w:st="on">Memphis</st1:place></st1:City>
code procedure of using the 10%/50 values from the 1996</font></tt><br>
<tt><font face="Courier New">> maps results in a PGA of 0.23g (for a stiff
soil site), which is</font></tt><br>
<tt><font face="Courier New">> substantially lower than the range of ground
motions estimated from the</font></tt><br>
<tt><font face="Courier New">> intensities reported in <st1:City w:st="on"><st1:place
w:st="on">Memphis</st1:place></st1:City> during the 1811-12 earthquake
sequence</font></tt><br>
<tt><font face="Courier New">> (0.34-0.65g for intensity VIII). A
similar value of PGA (0.22g) is found</font></tt><br>
<tt><font face="Courier New">> by taking the 5 Hz S.A. with 10%/50 and
dividing by 2.0, which is the</font></tt><br>
<tt><font face="Courier New">> factor relating PGA to 5 Hz S.A. derived for
M7.4-7.7 earthquakes from the</font></tt><br>
<tt><font face="Courier New">> average of the five attenuation relations.</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> Using a PGA that is 2/3 times the PGA with 2%
probability of exceedance</font></tt><br>
<tt><font face="Courier New">> in 50 years (2%/50), which corresponds to the
procedure used for spectral</font></tt><br>
<tt><font face="Courier New">> accelerations in the 2006 International
Building Code for the <st1:City w:st="on"><st1:place w:st="on">Memphis</st1:place></st1:City></font></tt><br>
<tt><font face="Courier New">> area, gives a PGA value of 0.50g for <st1:City
w:st="on"><st1:place w:st="on">Memphis</st1:place></st1:City> (stiff soil
site), which is</font></tt><br>
<tt><font face="Courier New">> in the range of the values estimated from the
1811-12 intensities. This</font></tt><br>
<tt><font face="Courier New">> is similar to the PGA value of 0.47g derived
from the 5 Hz S.A.in the IBC</font></tt><br>
<tt><font face="Courier New">> divided by a factor of 2.0 to convert
to PGA. So, there is evidence from</font></tt><br>
<tt><font face="Courier New">> intensity data that the ground motions
specified in the IBC have been</font></tt><br>
<tt><font face="Courier New">> experienced in <st1:City w:st="on"><st1:place
w:st="on">Memphis</st1:place></st1:City> during the 1811-12 earthquakes</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> In summary, the 1 Hz spectral accelerations
with a 10% probability of</font></tt><br>
<tt><font face="Courier New">> exceedance in 50 years, as used in the
current <st1:City w:st="on"><st1:place w:st="on">Memphis</st1:place></st1:City>
code, are</font></tt><br>
<tt><font face="Courier New">> substantially lower than the median 1 Hz
spectral accelerations expected</font></tt><br>
<tt><font face="Courier New">> for the next 1811-12 type earthquake. The
10%/50 value of PGA is probably</font></tt><br>
<tt><font face="Courier New">> lower than the ground shaking experienced in <st1:City
w:st="on"><st1:place w:st="on">Memphis</st1:place></st1:City> during the
1811-12</font></tt><br>
<tt><font face="Courier New">> earthquakes, based on intensity data.</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> The 1 Hz spectral accelerations specified in
the <st1:place w:st="on"><st1:PlaceName w:st="on">International</st1:PlaceName>
<st1:PlaceType w:st="on">Building</st1:PlaceType></st1:place></font></tt><br>
<tt><font face="Courier New">> Code (2/3 times the motions with a 2%
probability of exceedance in 50</font></tt><br>
<tt><font face="Courier New">> years) are similar to the median
1 Hz spectral accelerations expected</font></tt><br>
<tt><font face="Courier New">> for the next 1811-12 type earthquake. The PGA
with 2/3 times the value</font></tt><br>
<tt><font face="Courier New">> with 2%/50 is probably comparable to the PGA
experienced in <st1:City w:st="on"><st1:place w:st="on">Memphis</st1:place></st1:City>
from</font></tt><br>
<tt><font face="Courier New">> the 1811-12 earthquakes, based on intensity
data.</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> -Art</font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<tt><font face="Courier New">> Art Frankel</font></tt><br>
<tt><font face="Courier New">> <st1:country-region w:st="on"><st1:place
w:st="on">U.S.</st1:place></st1:country-region> Geological Survey</font></tt><br>
<tt><font face="Courier New">> MS 966, Box 25046</font></tt><br>
<tt><font face="Courier New">> DFC</font></tt><br>
<tt><font face="Courier New">> <st1:place w:st="on"><st1:City w:st="on">Denver</st1:City>,
<st1:State w:st="on">CO</st1:State> <st1:PostalCode w:st="on">80225</st1:PostalCode></st1:place></font></tt><br>
<tt><font face="Courier New">> phone: 303-273-8556</font></tt><br>
<tt><font face="Courier New">> fax: 303-273-8600</font></tt><br>
<tt><font face="Courier New">> email: <st1:PersonName w:st="on">afrankel@usgs.gov</st1:PersonName></font></tt><br>
<tt><font face="Courier New">></font></tt><br>
<br>
<br>
<tt><font face="Courier New">_______________________________________________</font></tt><br>
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<tt><font face="Courier New">https://geohazards.usgs.gov/mailman/listinfo/ceus-earthquake-hazards</font></tt></span></font><o:p></o:p></p>
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