[CEUS-earthquake-hazards] alternative hazard maps

Wed Feb 13 10:49:33 MST 2008

To the simple question, the simple answer is, at Paducah and Memphis,
the M7.7 at New Madrid will be felt the same day. Maybe the
spatial-temporal question is, will there follow soon, within, say, a few
years, a significant event at Charlestown? That would aid planning for
Charleston.

If disaster is 200 years away, there is no financial incentive to pay
more now. When the public hears it said that way, they would vote no to
expensive seismic retrofit when tornados are more likely to occur. 

 When you only have a few points to work with. . . statistics may not be
the right tool, even though it is required for presentation purposes.

Thank you for including me in your discussion chain.
Mike Carney 
Engineer.

________________________________

From: ceus-earthquake-hazards-bounces at geohazards.usgs.gov
[mailto:ceus-earthquake-hazards-bounces at geohazards.usgs.gov] On Behalf
Of Stephen C Harmsen
Sent: Thursday, February 07, 2008 8:34 AM
To: Eugene S Schweig
Cc: ceus-earthquake-hazards at geohazards.usgs.gov;
ceus-earthquake-hazards-bounces at geohazards.usgs.gov
Subject: Re: [CEUS-earthquake-hazards] alternative hazard maps

While Buddy's response does point out many relevant issues, I contend
that  Zhenming's question is not simple but is in fact baffling. 
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? 

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. 

Stephen Harmsen
Research Physical Scientist
USGS 
(303) 273 8567
mailing address: USGS, Denver Federal Center, 
MS 966, Box 25046, Denver, CO 80225

USGS office (for overnight deliveries):
1711 Illinois Street, Golden, CO 80401

Eugene S Schweig <schweig at usgs.gov> 
Sent by: ceus-earthquake-hazards-bounces at geohazards.usgs.gov 

02/07/2008 07:33 AM 

To
"ceus-earthquake-hazards at geohazards.usgs.gov"
<ceus-earthquake-hazards at geohazards.usgs.gov> 
cc
Subject
Re: [CEUS-earthquake-hazards] alternative hazard maps	

Zhenming, 

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. 

Buddy 
Fading into the Central U.S.Seismic Sunset 
__________________________________________________________________
Eugene Schweig
Chief Scientist
Earth Surface Processes Team
U.S. Geological Survey

Denver Office:
MS980 Federal Center                                      (303) 236-5344
Denver, CO 80225-0046                         Fax: (303) 236-5690

Memphis office:                                                
3876 Central Ave., Ste. 2                                 (901) 678-4974
MEMPHIS, TN  38152-3050                     Fax: (901) 678-4897
___________________________________________________________________

"Wang, Zhenming" <zmwang at email.uky.edu> 
Sent by: ceus-earthquake-hazards-bounces at geohazards.usgs.gov 

02/07/08 07:24 AM 

To
Arthur D Frankel <afrankel at usgs.gov>, Seth Stein
<seth at earth.northwestern.edu> 
cc
"ceus-earthquake-hazards at geohazards.usgs.gov"
<ceus-earthquake-hazards at geohazards.usgs.gov> 
Subject
Re: [CEUS-earthquake-hazards] alternative hazard maps	

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? 

Thanks. 

Zhenming 
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