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

Fri Apr 29 15:42:51 UTC 2011

After rereading the last paragraph in the ScienceNOW article several 
times, I agree with Sue. Stein's point is about the occurrence of 
earthquakes somewhere that are larger than any in the historical and 
paleoseismic records of that area. In such a case, as in Haiti, Wenchuan, 
and Tohoku, a pertinent question is whether the most recent probabilistic 
hazard assessment  of the area assumed the possibility of an earthquake at 
least as large as the big recent earthquake there. Since at least 1996 the 
CEUS parts of the USGS hazard maps have used Mmax values big enough that 
there have been no nasty surprises, either in the CEUS itself, in 
tectonically analogous areas worldwide, or in the sparse but growing 
paleoseismic record. Whether those CEUS values are really big enough to be 
Mmax we don't yet know how to tell. Actually we do know how to tell, but 
the approach is not particularly helpful: wait ten thousand years or so.

Rus Wheeler
-----------------------------------------
Rus Wheeler
research geologist
phone: (303) 273-8589
fax: (303) 273-8600
email: wheeler at usgs.gov

paper mail:
Russell L. Wheeler
U.S. Geological Survey
P.O. Box 25046, M.S. 966
Lakewood, CO 80225

physical address, FedEx, UPS:
1711 Illinois St., rm. 442
Golden, CO 80401

From:
"Susan Hough" <hough at gps.caltech.edu>
To:
"Central and Eastern U.S. Earthquake Hazards Listserve" 
<ceus-earthquake-hazards at geohazards.usgs.gov>
Cc:
"Central and Eastern U.S. Earthquake Hazards Listserve" 
<ceus-earthquake-hazards at geohazards.usgs.gov>
Date:
04/29/2011 05:37 AM
Subject:
Re: [CEUS-earthquake-hazards] Article on Central U.S. Earthquake hazard by 
expert panel
Sent by:
ceus-earthquake-hazards-bounces at geohazards.usgs.gov

I read and reread the ScienceNOW article looking for the word
"prediction," having seen Rus' comment before I read the article.  Seems
to me clear that Seth was commenting on the reliance on observed
seismicity alone to constrain hazard maps. I'm sure he talked to Kerr at
some length -- as always only a sound-bite makes it into a short article.
Rus' point is well taken: no one earthquake is a "failure" of a hazard
map, unless maybe the earthquake exceeds an Mmax value that was assumed in
generating the map.  More generally, though, I think the main point Seth
was making has been underscored by the quakes he mentioned.  I've made
this exact same argument in my own talks (most recently this evening),
usually by way of making the point that the short historical record can
lull people into a false sense of security.  But clearly it can go the
other way sometimes.  I.e., just thinking conceptually, there must be
areas that have been more active in the historic (or known prehistoric)
record than the average long-term rates.

Sue Hough

> The probabilistic methods that the USGS and other organizations use to
> estimate hazard are not predictions. Instead, the methods give estimates
> of the strength of shaking that we'd expect (at specified odds) to be
> exceeded in the next 50  years at some particular place. The specified
> odds are usually about one in ten or one in fifty. If a particular place
> is shaken at or above the estimated level, the cause could be either a 
big
> earthquake far away, or a smaller one nearby. Also, the expected shaking
> could occur at any time from tomorrow to 50 years from now...or not at
> all, if it beats the odds. Nothing in a probabilistic hazard estimate
> specifies the size, time, and location of the next big earthquake.
>
> Making a prediction and estimating the hazard are fundamentally 
different
> in purposes, assumptions, calculations, results, and uses. A failure to
> get either of them right has no bearing on the validity of the other 
one.
> -----------------------------------------
> Rus Wheeler
> research geologist
> phone: (303) 273-8589
> fax: (303) 273-8600
> email: wheeler at usgs.gov
>
> paper mail:
> Russell L. Wheeler
> U.S. Geological Survey
> P.O. Box 25046, M.S. 966
> Lakewood, CO 80225
>
> physical address, FedEx, UPS:
> 1711 Illinois St., rm. 442
> Golden, CO 80401
>
>
>
> From:
> Oliver Boyd <olboyd at usgs.gov>
> To:
> "ceus-earthquake-hazards at geohazards.usgs.gov"
> <ceus-earthquake-hazards at geohazards.usgs.gov>
> Date:
> 04/27/2011 10:09 AM
> Subject:
> [CEUS-earthquake-hazards] Article on Central U.S. Earthquake hazard by
> expert panel
> Sent by:
> ceus-earthquake-hazards-bounces at geohazards.usgs.gov
>
>
>
> Dear CEUS earthquake hazards email list subscribers,
> Below is a link to a short article about the findings of a National
> Earthquake Prediction Evaluation Council expert panel regarding central
> United States earthquake hazard.
>
> 
http://news.sciencemag.org/sciencenow/2011/04/expert-panel-central-us-faces.html

>
>
> Regards,
> Oliver
>
> --
>
> Oliver Boyd, Ph.D.
> Research Geophysicist
> U.S. Geological Survey
> 3876 Central Ave
> Memphis, TN
> Phone: (901) 678-3463
> FAX: (901) 678-4897_______________________________________________
> CEUS-Earthquake-Hazards mailing list
> CEUS-Earthquake-Hazards at geohazards.usgs.gov
> https://geohazards.usgs.gov/mailman/listinfo/ceus-earthquake-hazards
>
>
> _______________________________________________
> CEUS-Earthquake-Hazards mailing list
> CEUS-Earthquake-Hazards at geohazards.usgs.gov
> https://geohazards.usgs.gov/mailman/listinfo/ceus-earthquake-hazards
>

_______________________________________________
CEUS-Earthquake-Hazards mailing list
CEUS-Earthquake-Hazards at geohazards.usgs.gov
https://geohazards.usgs.gov/mailman/listinfo/ceus-earthquake-hazards

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://geohazards.usgs.gov/pipermail/ceus-earthquake-hazards/attachments/20110429/32bffce3/attachment.html>