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

[Michael Blanpied]

Rus,

Another issue is that Seth's quotation implies that the Haiti hazard was mapped using the same techniques as the USGS uses:  
   "The same sort of risk evaluation methodology that is used by USGS 'has had a series of spectacular failures around the world in the last 5 years—Haiti, Wenchuan [China], and Japan,' [Stein] says.

That is simply not the case, at least in the case of Haiti.

For Haiti, the only existing hazard map was from GSHAP, which used broad-brush approach to global hazard estimation based on smoothed instrumental seismicity. There was not much hazard mapped in Haiti because the recent seismicity rates have been low. The Enriquillo, Septentrional and other faults were recognized, and it was known that Port au Prince had suffered large pre-instrumental quakes, but these were not taken into account. This was NOT "the same sort of methodology used by USGS."

Even a back-of-the-envelope calculation taking into account several mm/year on the Enriquillo fault puts a band of high hazard right through the strongly shaken region. Hazard maps based on USGS methods was  by Art Frankel, Eric Calais and colleagues, see: http://pubs.usgs.gov/of/2010/1067/

What Haiti illustrated was not a failure of modern seismic hazard mapping methods, but that hazard maps for some regions of the world are not up to modern standards. Efforts like Art's and Eric's, and the work of GEM (http://www.globalquakemodel.org/), are working to improve that situation.

Mike


On Apr 27, 2011, at 5:56 PM, Russell L Wheeler wrote:

> 
> Some people may have interpreted the end of the ScienceNOW article to mean that the USGS hazard evaluation methodology failed to predict the Haiti, Wenchuan, and Japan earthquakes. The methodology was not designed to predict the time, size and location of the next big earthquake, and the USGS does not use it that way. 
> 
> 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_______________________________________________
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