<br><font size=2 face="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.</font>
<br>
<br><font size=2 face="sans-serif">Emitt</font>
<br><font size=2 face="sans-serif">________________________________________<br>
Emitt C. Witt III, P.H.<br>
Director, Mid-Continent Geographic Science Center<br>
1400 Independence Road<br>
Rolla, Missouri 65401<br>
573-308-3679<br>
573-308-3794 FAX<br>
http://mcmcweb.er.usgs.gov/mcgsc<br>
</font>
<br>
<br>
<br>
<table width=100%>
<tr valign=top>
<td width=40%><font size=1 face="sans-serif"><b>Allen Jones <jonesal@myuw.net></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">02/15/2008 11:14 AM</font>
<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">Re: [CEUS-earthquake-hazards] reply
to Joe Tomasello; buildings codes and earthquake hazard</font></table>
<br>
<table>
<tr valign=top>
<td>
<td></table>
<br></table>
<br>
<br>
<br><font size=2><tt>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.<br>
<br>
Allen Jones<br>
________________________<br>
Allen Jones, PE, PhD<br>
South Dakota State University<br>
Department of Civil Engineering<br>
CEH 148, Box 2219<br>
Brookings, SD 57006<br>
<br>
Direct: 605-688-6467<br>
Fax: 605-688-6476<br>
<br>
On Fri, 15 Feb 2008, Arthur D Frankel wrote:<br>
<br>
> Zhenming,<br>
><br>
> I am sure many people on the bulletin board are getting tired
of these<br>
> exchanges.<br>
><br>
> I presented similar comparisons at the Applied Technology Council<br>
> workshop in Memphis in March 2005. As I recall, you and Joe
Tomasello<br>
> were in attendance. So I think you have seen these comparisons.<br>
><br>
> Of course, I don't see any contradiction in what I've said.
I think it<br>
> is reasonable to compare code values with the expected ground motions
from<br>
> the next 1811-12 type earthquake and with ground motions estimated
for the<br>
> 1811-12 earthquakes using intensity observations.<br>
><br>
> I think further discussion between us on these issues should
be made off<br>
> of the bulletin board.<br>
><br>
> -Art<br>
><br>
><br>
> Art Frankel<br>
> U.S. Geological Survey<br>
> MS 966, Box 25046<br>
> DFC<br>
> Denver, CO 80225<br>
> phone: 303-273-8556<br>
> fax: 303-273-8600<br>
> email: afrankel@usgs.gov<br>
><br>
><br>
><br>
> "Wang, Zhenming" <zmwang@email.uky.edu><br>
> 02/15/2008 08:35 AM<br>
><br>
> To<br>
> Arthur D Frankel <afrankel@usgs.gov><br>
> cc<br>
> James Cobb <cobb@uky.edu>, "Keifer, John D" <kiefer@email.uky.edu>,<br>
> "ceus-earthquake-hazards@geohazards.usgs.gov"<br>
> <ceus-earthquake-hazards@geohazards.usgs.gov><br>
> Subject<br>
> RE: [CEUS-earthquake-hazards] reply to Joe Tomasello; buildings
codes<br>
> and earthquake hazard<br>
><br>
><br>
><br>
><br>
><br>
><br>
> Art,<br>
><br>
> This is the first time we see these comparisons:<br>
><br>
> ?When I talk to code committees and other groups, I compare the relative<br>
> level of protection that designing to different probability levels
of<br>
> ground shaking will provide to buildings. This can be assessed
by<br>
> comparing the ground-motion values for the probability levels in the<br>
> building codes to the median ground motions expected when the next
1811-12<br>
> type New Madrid earthquake occurs and by comparing code values to<br>
> intensities observed in the Memphis area from the 1811-12 earthquakes.?<br>
><br>
> The selected design ground motion should be consistent with the scientific<br>
> facts. However, these comparisons seem to be contradictory to your
early<br>
> statements:<br>
> 1. ?In fact, we release seismic hazard curves
(a range of ground<br>
> motion, from 0.0 to 10g or larger) for a grid of sites across the
nation,<br>
> so that users can calculate the ground motions at any probability
level<br>
> they choose.? ?It should also be reiterated that the national seismic<br>
> hazard maps are based on the average hazard curves from a variety
of input<br>
> models and attenuation relations; they are not worst-case maps.?<br>
> 2. ?It is not correct to compare the intensity
observations from<br>
> 1811-1812 with the probabilistic hazard maps that also include the
hazard<br>
> from earthquakes closer to St. Louis.?<br>
><br>
> Thanks.<br>
><br>
> Zhenming<br>
><br>
> From: ceus-earthquake-hazards-bounces@geohazards.usgs.gov<br>
> [mailto:ceus-earthquake-hazards-bounces@geohazards.usgs.gov] On Behalf
Of<br>
> Arthur D Frankel<br>
> Sent: Thursday, February 14, 2008 3:35 PM<br>
> To: ceus-earthquake-hazards@geohazards.usgs.gov<br>
> Subject: [CEUS-earthquake-hazards] reply to Joe Tomasello; buildings
codes<br>
> and earthquake hazard<br>
><br>
><br>
> Joe,<br>
><br>
> The USGS policy is to support the process of the Building Seismic
Safety<br>
> Council (BSSC) establishing probability levels and design procedures
for<br>
> the national model building codes, such as the International Building<br>
> Code. The BSSC membership consists of a large group of engineers
and<br>
> stakeholders. The BSSC is a council of the National Institute of Building<br>
> Sciences. The code development process of the BSSC is funded by FEMA.
The<br>
> design procedures are published in the NEHRP Recommended Provisions
for<br>
> the Development of Seismic Regulations for New Buildings, which is
written<br>
> by the BSSC/NIBS and published by FEMA.<br>
><br>
> I think a key responsibility of the USGS is to provide the best scientific<br>
> information to decision makers. Part of this scientific information
is<br>
> assessment of the ground motions from the 1811-12 earthquakes and<br>
> estimation of the ground motions for the next 1811-12 type earthquake.<br>
><br>
> When I talk to code committees and other groups, I compare the relative<br>
> level of protection that designing to different probability levels
of<br>
> ground shaking will provide to buildings. This can be assessed
by<br>
> comparing the ground-motion values for the probability levels in the<br>
> building codes to the median ground motions expected when the next
1811-12<br>
> type New Madrid earthquake occurs and by comparing code values to<br>
> intensities observed in the Memphis area from the 1811-12 earthquakes.<br>
><br>
> For example, the value of ground motions around 1 Hz with a 10%<br>
> probability of exceedance in 50 years (10%/50) is substantially lower
than<br>
> the median 1 Hz ground motion expected for the next 1811-12 type<br>
> earthquake. The new Memphis code adopted in 2006 uses the 10%/50
year<br>
> ground motions from the 1996 vintage of the national maps (the 2002
maps<br>
> are higher). Here I am considering 1 Hz spectral accelerations
(S.A.),<br>
> which are used for the design of buildings with about 10 stories.
For a<br>
> site in Memphis (35.15 N; 90.05 W), the 10%/50 value of 1 Hz
spectral<br>
> acceleration is 0.16g (from the 1996 maps and using an amplification<br>
> factor of 2.4 for class D stiff-soil site relative to firm-rock site
from<br>
> the NEHRP amplification factors). This is much lower than the
median 1 Hz<br>
> S.A. of 0.36g expected in Memphis from a scenario earthquake with
moment<br>
> magnitude 7.7 located on the portion of the current New Madrid seismicity<br>
> trend northwest of Memphis (using the stiff-soil amplification factor
from<br>
> the NEHRP factors). This calculation of the expected spectral acceleration<br>
> is based on the average of the five attenuation relations used in
the 2002<br>
> national maps. If the next large New Madrid earthquake was a
moment<br>
> magnitude 7.4, the calculated median 1 Hz S.A. at Memphis would be
0.29g<br>
> for a stiff-soil site, still much higher than the 10%/50 value (0.16g)<br>
> from the 1996 maps.<br>
><br>
> The 10%/50 values for 1 Hz S.A. from the 2002 hazard maps would still
be<br>
> significantly lower than the scenario ground motions. For 5 Hz S.A.,
the<br>
> expected values of the median ground motions for a M7.7 earthquake
are<br>
> more sensitive to assumptions on the nonlinearity and attenuation
of<br>
> sediments in the Mississippi Embayment.<br>
><br>
> The International Building Code (IBC) uses spectral accelerations
that are<br>
> 2/3 times the values with a 2% probability of exceedance in 50 years
for<br>
> most of the nation (there are some areas where IBC uses the median<br>
> deterministic ground motions, depending on the level of the probabilistic<br>
> motions). For 1 Hz S.A., the 2006 IBC specifies a value of 0.42g for<br>
> Memphis (stiff-soil site). This is similar to the median value of
0.36g<br>
> expected for a M7.7 earthquake (see above).<br>
><br>
> In my presentations, I also compare the code values to the ground
motions<br>
> estimated from intensity reports in the Memphis area from past<br>
> earthquakes. Here I use peak ground accelerations (PGA) rather
than<br>
> spectral accelerations, because intensities are generally correlated
in<br>
> the literature with PGA?s or peak ground velocities.<br>
><br>
> Intensities in the Memphis area during the 1811-12 earthquakes have
been<br>
> assigned as intensity VIII by Hough et al. (2000) and as intensity
X by<br>
> Johnston (1996), depending on their interpretation of earthquake effects.<br>
> Intensity VIII corresponds to a peak ground acceleration between about<br>
> 0.34 and 0.65g, based on the work David Wald did for Shakemap. This
range<br>
> is consistent with the calculated median PGA at Memphis of 0.39g for
a<br>
> M7.7 earthquake determined from the average of 5 attenuation relations<br>
> used in the 2002 hazard maps (using the NEHRP amplification factors).
The<br>
> calculated PGA for a M7.4 earthquake is 0.32g, close to the range
of the<br>
> PGA?s estimated for intensity VIII.<br>
><br>
> The new Memphis code procedure of using the 10%/50 values from the
1996<br>
> maps results in a PGA of 0.23g (for a stiff soil site), which is<br>
> substantially lower than the range of ground motions estimated from
the<br>
> intensities reported in Memphis during the 1811-12 earthquake sequence<br>
> (0.34-0.65g for intensity VIII). A similar value of PGA (0.22g)
is found<br>
> by taking the 5 Hz S.A. with 10%/50 and dividing by 2.0, which is
the<br>
> factor relating PGA to 5 Hz S.A. derived for M7.4-7.7 earthquakes
from the<br>
> average of the five attenuation relations.<br>
><br>
> Using a PGA that is 2/3 times the PGA with 2% probability of exceedance<br>
> in 50 years (2%/50), which corresponds to the procedure used for spectral<br>
> accelerations in the 2006 International Building Code for the Memphis<br>
> area, gives a PGA value of 0.50g for Memphis (stiff soil site), which
is<br>
> in the range of the values estimated from the 1811-12 intensities.
This<br>
> is similar to the PGA value of 0.47g derived from the 5 Hz S.A.in
the IBC<br>
> divided by a factor of 2.0 to convert to PGA. So, there is evidence
from<br>
> intensity data that the ground motions specified in the IBC have been<br>
> experienced in Memphis during the 1811-12 earthquakes<br>
><br>
> In summary, the 1 Hz spectral accelerations with a 10% probability
of<br>
> exceedance in 50 years, as used in the current Memphis code, are<br>
> substantially lower than the median 1 Hz spectral accelerations expected<br>
> for the next 1811-12 type earthquake. The 10%/50 value of PGA is probably<br>
> lower than the ground shaking experienced in Memphis during the 1811-12<br>
> earthquakes, based on intensity data.<br>
><br>
> The 1 Hz spectral accelerations specified in the International Building<br>
> Code (2/3 times the motions with a 2% probability of exceedance in
50<br>
> years) are similar to the median 1 Hz spectral accelerations
expected<br>
> for the next 1811-12 type earthquake. The PGA with 2/3 times the value<br>
> with 2%/50 is probably comparable to the PGA experienced in Memphis
from<br>
> the 1811-12 earthquakes, based on intensity data.<br>
><br>
> -Art<br>
><br>
><br>
><br>
> Art Frankel<br>
> U.S. Geological Survey<br>
> MS 966, Box 25046<br>
> DFC<br>
> Denver, CO 80225<br>
> phone: 303-273-8556<br>
> fax: 303-273-8600<br>
> email: afrankel@usgs.gov<br>
><br>
<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>
</tt></font>
<br>