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<DIV><FONT color=#0000ff> I apologize that Dr. Stein needed to
correct my misplaced emphasis for my point to be clarified. I should have
delayed my comments until properly proofed and then made the request about
recurrence. </FONT></DIV>
<DIV><FONT color=#0000ff> The issue for the recurrence was that
the quoted statement ("we don't need to worry about a Major New Madrid
earthquake for another 300 years") misrepresents the 500-year return period
(Poisson's 9.5% probability of exceedance in 50 years) of a Major event.
The quote suggests that the event is NOT likely to occur until another 300
years have passed. In fact over the 196 years since the Great New Madrid
Series, there was a 32% probability of one or more Major events. Over the
full 500 years until 2312 there is a 63% probability of one or more Major
events. This is much different than the public's perception (and
the intent for using the quote) of the binary instance, an Off / On
toggle - the improper view that there is almost no chance of such an event
until return period has been approached. </FONT></DIV>
<DIV><FONT color=#0000ff> I grant that 11 times the energy needs to
be stored to transform a Strong M6.3 to a Major M7.0. The 100 - 150
year recurrence that Dr. Stein noted, or 33% probability of exceedance
in 50 years, is not an absolute, binary return interval. The 113
years since the 1895 event had a 60% probability that one or more low
M6 or greater events would have occurred. I would again state that a
Strong New Madrid event is overdue. Yet Palmdale, CA shows that we
cannot trust seeming periodicity. </FONT></DIV>
<DIV><FONT color=#0000ff> So thanks, Dr. Stein, for correcting my
misplaced emphasis so that the real argument concerning RECURRENCE that I
failed to make could be cited. </FONT></DIV>
<DIV><FONT color=#0000ff> I ask all to please consider
using "x% probability of exceedance for one or more magnitude-specified events
in 50 years" (or whatever interval that one would choose). Like weather
forecasts of a "30% chance of rain tomorrow," the public can understand the
likelihood of a hazard over a time interval. </FONT></DIV>
<DIV><FONT color=#0000ff> I appreciate the comments again of
Zhenming and restate the following. With so much to learn about
earthquakes, we all should take care to be consistent and not misstate what is
understood. </FONT></DIV>
<DIV><FONT color=#0000ff> [Further, I will heed my own advise
to read and correct my own statements before dashing them off.]</FONT></DIV>
<DIV><FONT color=#0000ff></FONT> </DIV>
<DIV>Greg <BR>Greg Hempen, PhD, PE, RG</DIV>
<DIV>URS Corporation, <A href="mailto:greg_hempen@urscorp.com"><FONT
color=#000000>greg_hempen@urscorp.com</FONT></A> <BR></DIV>
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style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #0000ff 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=seth@earth.northwestern.edu
href="mailto:seth@earth.northwestern.edu">Seth Stein</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=ceus-earthquake-hazards@geohazards.usgs.gov
href="mailto:ceus-earthquake-hazards@geohazards.usgs.gov">Central and Eastern
U.S. Earthquake Hazards Listserve</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, May 19, 2008 3:42 PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [CEUS-earthquake-hazards]
Comment on "major" earthquake</DIV>
<DIV><BR></DIV>The term "major" earthquake is typically used in textbooks,
etc. for <BR>magnitude greater than 7<BR><BR><A
href="http://en.wikipedia.org/wiki/Richter_magnitude_scale">http://en.wikipedia.org/wiki/Richter_magnitude_scale</A><BR><BR>In
the New Madrid zone the last was in 1812. A magnitude 6 occurs on <BR>average
about every 100-150 years.<BR><BR>It's interesting to read the accounts of the
1895 (M estimated as <BR>6.0-6.6) earthquake, the largest since 1812<BR><BR><A
href="http://earthquake.usgs.gov/regional/states/events/1895_10_31.php">http://earthquake.usgs.gov/regional/states/events/1895_10_31.php</A><BR><BR>and
the 1968 (M ~ 5.5) earthquake<BR><BR><A
href="http://earthquake.usgs.gov/regional/states/events/1968_11_09.php">http://earthquake.usgs.gov/regional/states/events/1968_11_09.php</A><BR><BR>In
both, most of the damage occurred in an area close to the epicenter <BR>of
intensity VII (moderate damage) consisting of "downed chimneys, <BR>cracked
walls, shattered windows, and broken plaster," and lesser <BR>effects further
away.<BR><BR>This is obviously not good, but it's probably not what the public
would <BR>regard as a "major" disaster. It's worth noting that if everyone
<BR>involved had had earthquake insurance with a 15% deductible<BR><BR><A
href="http://www.stltoday.com/stltoday/news/columnists.nsf/savvyconsumer/story/FA8B07211D6155BD8625743600105DFE?OpenDocument">http://www.stltoday.com/stltoday/news/columnists.nsf/savvyconsumer/story/FA8B07211D6155BD8625743600105DFE?OpenDocument</A><BR><BR>few
would have collected.<BR><BR>Of course one could conceive of locations in the
New Madrid zone where <BR>if such an earthquake happens to hit damage would be
greater<BR><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: <A
href="mailto:seth@earth.northwestern.edu">seth@earth.northwestern.edu</A><BR><A
href="http://www.earth.northwestern.edu/people/seth">http://www.earth.northwestern.edu/people/seth</A><BR><BR><BR>>
<BR>> With so much to learn about earthquakes, we all
should take care to <BR>> be consistent and not overstate what is
known. A quoted seismologist in <BR>> discussing the 18 APR 08 Mount
Carmel, IL event said "we don't to worry <BR>> about a */MAJOR
/*[highlighted for emphasis] New Madrid earthquake for <BR>> another 300
years." It is my understanding that we are overdue for a <BR>> low M6
event (yet not 100% likelihood in 10 years) in the New Madrid <BR>>
region. A major event and a low M6 is too casual of use and certainly
<BR>> feeds the misinformation to the public, because of a slip of the
tongue. <BR>>
<BR>_______________________________________________<BR>CEUS-Earthquake-Hazards
mailing list<BR><A
href="mailto:CEUS-Earthquake-Hazards@geohazards.usgs.gov">CEUS-Earthquake-Hazards@geohazards.usgs.gov</A><BR><A
href="https://geohazards.usgs.gov/mailman/listinfo/ceus-earthquake-hazards">https://geohazards.usgs.gov/mailman/listinfo/ceus-earthquake-hazards</A></BLOCKQUOTE></BODY></HTML>