<br><font size=2 face="sans-serif">While Buddy's response does point out
many relevant issues, I contend that Zhenming's question is not simple
but is in fact baffling.</font>
<br><font size=2 face="sans-serif">How often are ground motions observed
depends on how many observers are present. The populations of these cities
increase with time, at least that is the trend for a few centuries. Civil
defense measures may evolve with time and we might hope that before the
next NMSZ major event occurs some effort will be made to evacuate less
seismically resistant buildings. People who live and work in these identified
buildings may leave these cities for awhile, so simple population projections
might not be valid. If we are talking about 200 years in the future, we
should hope that continued science and technology improvements will lessen
the number of observers at least the number of casualties. Those who want
to ride the wave should be welcomed to do so after sober assessment of
their odds. Then, there is the likelihood of several events in a short
time span. Does an observation of each count as one or as several? What
about observations of aftershocks? If the observer dies before he/she has
a chance to report, does his/her observation count? Do pets' observations
count?</font>
<br>
<br><font size=2 face="sans-serif">In the NMSZ events of 1811-1812 most
people lived and worked in 1-story buildings generally wood frame construction
(how much sod?). Now, the built environment is much different and the number
of hostages to vagaries of tall building response has increased. While
there is considerable inertia to seismic resistant design in many counties
it is difficult to predict how adequate the nation's and individual states'
response to the seismic threat will be over the next few centuries. The
difficulty lies in the many societal pressures that have been discussed
in these various emails, what resources are dedicated to which threats,
and whose voice is heard. These are indeed unpredictable factors. </font>
<br><font size=2 face="sans-serif"><br>
Stephen Harmsen<br>
Research Physical Scientist<br>
USGS <br>
(303) 273 8567<br>
mailing address: USGS, Denver Federal Center, <br>
MS 966, Box 25046, Denver, CO 80225<br>
<br>
USGS office (for overnight deliveries):<br>
1711 Illinois Street, Golden, CO 80401<br>
</font>
<br>
<br>
<br>
<table width=100%>
<tr valign=top>
<td width=40%><font size=1 face="sans-serif"><b>Eugene S Schweig <schweig@usgs.gov></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">02/07/2008 07:33 AM</font>
<td width=59%>
<table width=100%>
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<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] alternative
hazard maps</font></table>
<br>
<table>
<tr valign=top>
<td>
<td></table>
<br></table>
<br>
<br>
<br><font size=2 face="sans-serif"><br>
Zhenming,</font><font size=3> <br>
</font><font size=2 face="sans-serif"><br>
While your question is simple, it is also misleading. If we could
count on M 7.7 earthquakes happenning every 500 years, and we could count
on the ground motions always be the same at each of these locations for
a New Madrid event, and if a repeat of 1811-1812 were the only thing that
could cause that level of ground motions at each location, our leaders
could go to bed happy that it would be at lest 200 hundred years before
they had to start building safe buildings. Sadly, none of this is
true. We have little information on the regularity of earthquake
timing. We know there can be significant variation in the ground
motions generated by the same size earthquake from even to event because
of a number of factors. We also know that other earthquakes besides
a repeat of the 1811-1812 earthquakes may contribute to the possibility
of large ground motions, particularly with increasing distance from New
Madrid. So while the question is simple, the answer is not, which
I am sure you already know.</font><font size=3> <br>
</font><font size=2 face="sans-serif"><br>
Buddy</font><font size=3> </font><font size=2 face="sans-serif"><br>
Fading into the Central U.S.Seismic Sunset</font><font size=3> </font><font size=2 face="sans-serif"><br>
__________________________________________________________________<br>
Eugene Schweig<br>
Chief Scientist<br>
Earth Surface Processes Team<br>
U.S. Geological Survey<br>
<br>
Denver Office:<br>
MS980 Federal Center
(303)
236-5344<br>
Denver, CO 80225-0046
Fax: (303) 236-5690<br>
<br>
Memphis office:
<br>
3876 Central Ave., Ste. 2
(901) 678-4974<br>
MEMPHIS, TN 38152-3050
Fax: (901) 678-4897<br>
___________________________________________________________________<br>
</font><font size=3><br>
<br>
<br>
</font>
<table width=100%>
<tr valign=top>
<td width=37%><font size=1 face="sans-serif"><b>"Wang, Zhenming"
<zmwang@email.uky.edu></b> <br>
Sent by: ceus-earthquake-hazards-bounces@geohazards.usgs.gov</font><font size=3>
</font>
<p><font size=1 face="sans-serif">02/07/08 07:24 AM</font><font size=3>
</font>
<td width=62%>
<br>
<table width=100%>
<tr valign=top>
<td width=13%>
<div align=right><font size=1 face="sans-serif">To</font></div>
<td width=86%><font size=1 face="sans-serif">Arthur D Frankel <afrankel@usgs.gov>,
Seth Stein <seth@earth.northwestern.edu></font><font size=3> </font>
<tr valign=top>
<td>
<div align=right><font size=1 face="sans-serif">cc</font></div>
<td><font size=1 face="sans-serif">"ceus-earthquake-hazards@geohazards.usgs.gov"
<ceus-earthquake-hazards@geohazards.usgs.gov></font><font size=3>
</font>
<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] alternative
hazard maps</font></table>
<br>
<br>
<table width=100%>
<tr valign=top>
<td width=49%>
<td width=50%></table>
<br></table>
<br><font size=3><br>
</font><font size=2 color=#000080 face="Arial"><br>
</font><font size=3> </font><font size=2 color=#000080 face="Arial"><br>
Here is a simple question for every one: If an M7.7 earthquake occurs every
500 years in the New Madrid seismic zone, how often will the ground motion
generated by that earthquake be observed in Memphis, St. Louis, or Paducah?</font><font size=3>
</font><font size=2 color=#000080 face="Arial"><br>
</font><font size=3> </font><font size=2 color=#000080 face="Arial"><br>
Thanks.</font><font size=3> </font><font size=2 color=#000080 face="Arial"><br>
</font><font size=3> </font><font size=2 color=#000080 face="Arial"><br>
Zhenming <br>
</font><font size=3> </font><font size=2><tt>_______________________________________________<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>