[CEUS-earthquake-hazards] FW: Reporton estimatingmaximum magnitude in the Central and Eastern US.

Mon Jun 1 17:43:21 GMT 2009

Dear John, I wish I could. I'd do away with probability altogether. But
engineers demand it. It gives them and their clients a pretension that they
are saving money. So I compromised. Just so that they do the important things
right. However, if you can persuade them otherwise, go ahead. Ellis   

-----Original Message-----
From: ceus-earthquake-hazards-bounces at geohazards.usgs.gov
[mailto:ceus-earthquake-hazards-bounces at geohazards.usgs.gov] On Behalf Of
Keifer, John D
Sent: Friday, May 29, 2009 4:10 PM
To: Central and Eastern U.S. Earthquake Hazards Listserve
Subject: Re: [CEUS-earthquake-hazards] FW: Reporton estimatingmaximum
magnitude in the Central and Eastern US.

Thanks Ellis, I would agree.  My only problem is that you suggest the use of
Probability for a cost/risk benefit for non critical construction.  In your
own excellent paper in Engineering Geology, vol.65, 2002, you state "Seismic
probabilities have a range of error that makes them totally meaningless for
application to the lifetime of structures. I agree.  So why use probability
at all in an area like New Madrid, where there is already so much
uncertainty?

John

-----Original Message-----
From: ceus-earthquake-hazards-bounces at geohazards.usgs.gov
[mailto:ceus-earthquake-hazards-bounces at geohazards.usgs.gov] On Behalf Of
Krinitzsky, Ellis L ERDC-GSL-MS Emeritus
Sent: Thursday, May 28, 2009 2:13 PM
To: Central and Eastern U.S. Earthquake Hazards Listserve
Subject: Re: [CEUS-earthquake-hazards] FW: Report on estimatingmaximum
magnitude in the Central and Eastern US.

John, Critical means the consequences of failure are intolerable. For that
the design should be based on a simple deterministic assessment, not
complicated by errors from the unknowns in probability. For non-critical
construction, or non-critical elements in a critical structure, probability
can be used for a cost/risk benefit.  But keep in mind that probability is
not a reliable method. It is too full of uncertainties that it pretends to
give values for, but the values remain uncertain.

Ellis 

-----Original Message-----
From: ceus-earthquake-hazards-bounces at geohazards.usgs.gov
[mailto:ceus-earthquake-hazards-bounces at geohazards.usgs.gov] On Behalf Of
Keifer, John D
Sent: Wednesday, May 27, 2009 10:06 AM
To: Central and Eastern U.S. Earthquake Hazards Listserve
Subject: Re: [CEUS-earthquake-hazards] FW: Report on estimatingmaximum
magnitude in the Central and Eastern US.

Ellis, it would still seem that everything depends on the criticality of the
structure. How would you define criticality.  Also, while you are right that
no one can tell you that a 10,000 year earthquake won't happen tomorrow, the
longer the time span the lower the probability that it will happen tomorrow.

John

-----Original Message-----
From: ceus-earthquake-hazards-bounces at geohazards.usgs.gov
[mailto:ceus-earthquake-hazards-bounces at geohazards.usgs.gov] On Behalf Of
Krinitzsky, Ellis L ERDC-GSL-MS Emeritus
Sent: Tuesday, May 26, 2009 1:53 PM
To: Central and Eastern U.S. Earthquake Hazards Listserve
Subject: Re: [CEUS-earthquake-hazards] FW: Report on estimating maximum
magnitude in the Central and Eastern US.

That is a wrong assumption. For a critical structure, protection must be
regardless of time. That is the essential quality of a deterministic
evaluation. 

-----Original Message-----
From: ceus-earthquake-hazards-bounces at geohazards.usgs.gov
[mailto:ceus-earthquake-hazards-bounces at geohazards.usgs.gov] On Behalf Of
Wang, Zhenming
Sent: Thursday, May 07, 2009 12:11 PM
To: Central and Eastern U.S. Earthquake Hazards Listserve
Subject: [CEUS-earthquake-hazards] FW: Report on estimating maximum magnitude
in the Central and Eastern US.

Time is a fundamental element that must be considered in any activity.

-----Original Message-----
From: Krinitzsky, Ellis L ERDC-GSL-MS Emeritus
[mailto:Ellis.L.Krinitzsky at usace.army.mil] 
Sent: Thursday, May 07, 2009 10:01 AM
To: Central and Eastern U.S. Earthquake Hazards Listserve
Cc: Wang, Zhenming
Subject: RE: [CEUS-earthquake-hazards] Report on estimating maximum magnitude
in the Central and Eastern US.

Everything depends on the criticality of the structure. If the structure is
critical (the consequences of failure are intolerable) then one must design
for the maximum earthquake regardless of temporality. Otherwise, it is proper
to design on a cost-risk basis.

Nobody can say that a 1,000-year earthquake or a 10,000-year, both based on
150-year record, will not happen tomorrow. The 10,000-year earthquake,
assuming the time estimate has any meaning, could just as well be more likely
to happen.

Ellis Krinitzsky
Corps of Engineers, ERDC, Vicksburg  

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