[CEUS-earthquake-hazards] Article on Central U.S. Earthquake hazard by expert panel

Oliver Boyd olboyd at usgs.gov
Fri Apr 29 11:41:07 UTC 2011


------ Forwarded Message
From: Seth Stein <seth at earth.northwestern.edu>
Organization: Northwestern University
Date: Thu, 28 Apr 2011 17:35:26 -0500
To: Oliver Boyd DOI/GD/Golden <olboyd at usgs.gov>
Subject: for listserv

Assessing how well earthquake hazard maps perform is an interesting
question.

There's a thoughtful discussion in Nature
"Shake-up time for Japanese seismology"
(Geller, Nature, 472, 407-409, 28 April 2011)

http://www.nature.com/nature/journal/v472/n7344/full/nature10105.html

about the Japanese hazard mapping and the March 2011 M 9.1 earthquake
off Tohoku.

Its assessment is

"The regions assessed as most dangerous are the zones of three hypothetical
'scenario earthquakes' (Tokai, Tonankai and Nankai; see map).
However, since 1979, earthquakes that caused 10 or more fatalities in
Japan actually occurred in places assigned a relatively low probability.
This discrepancy -- the latest in a string of negative results for
the characteristic earthquake model and its cousin, the seismic-gap model
-- strongly suggests that the hazard map and the methods used to produce
it are flawed and should be discarded."

For the Haiti, China, and North Africa hazard map failures, see

www.earth.northwestern.edu/people/seth/research/eqrec.html

The failures illustrate that hazard maps often have very large
uncertainties,
which are often not recognized by their users.

As Mike said for Haiti, new hazard maps are sometimes made after a big
earthquake
that the earlier maps missed. That's led to the observation that sometimes
the main thing one learns from a hazard map is the year it was made.
Statisticians
refer to such a postiori changes to a model as "Texas sharpshooting",
in which one shoots at the barn and draws circles around the bullet holes.
The question is whether and how much better the new map predicts than
the older one,
which may take a while - sometimes hundreds of years - to assess.





-- 
Seth Stein
William Deering Professor
Department of Earth and Planetary Sciences
1850 Campus Drive
Northwestern University, Evanston, IL 60208
(847) 491-5265 FAX: (847) 491-8060 E-MAIL: seth at earth.northwestern.edu
http://www.earth.northwestern.edu/people/seth


------ End of Forwarded Message




More information about the CEUS-Earthquake-Hazards mailing list