I have been following these discussions with some interest, and I'd like to add some thoughts from
an insurance perspective. To quote from earlier correspondence,  

"The purpose of finding this information is to feed training programs for voluntary field
operators (non technical persons) in emergency management. For enabling
them to understand the hazard zonation in areas that they are assigned to,
and be prepared to expect disasters in accordance, as well as to able to
appreciate the extent of an event, the issue of scales came up."

First it needs to be remembered that there can be more than one type of hazard potentially
affecting any one area.  Each will have a different frequency and severity as well as areal extent.
 
To take a very basic example, a builder erects scaffolding.  One hazard is that a hammer falls off
the scaffolding, another is that the scaffolding blows down.  In each case the area exposed to the
hazard is different, but if there is no person or property in that area then there is no risk of
injury or damage.
If a workman walks under the scaffolding then he is exposed to the risk of injury (exposure), but
if he wears a helmet he is less vulnerable to the falling hammer (vulnerability) though he, and
many others,  could be injured if the scaffolding blows over (unless a warning is given and the
area is evacuated to remove the exposure).

The point is that there is no risk unless the three elements of hazard, vulnerability and exposure
are all present and that the amount of exposure and vulnerability will depend on the nature of the
hazard. (The so called "Risk Triangle")

Insurers now make widespread use of hazard maps with a different map for each peril or type of
hazard.  They then aggregate these taking into account the different probabilities of each hazard,
and work out loss potential ratios based on the exposure and vulnerability.  Such maps are
available at a price for most of the world from organisations like EQE and RMS and are widely used
by the insurance and reinsurance industry.  Perhaps governments should be using them too?

Thanks for your time.


Prof. David Crichton, <[log in to unmask]>
1 Quarryknowe Crescent
 INCHTURE, Perthshire, Scotland. PH14 9RH
Tel;  +44 (0) 1828 686493
Fax and voicemail;  +44 (0) 1828 686961
Why not join the Natural Hazards Network?
http://www.mailbase.ac.uk/lists/natural-hazards-disasters/

----------
> From: Mohammed Dore <[log in to unmask]>
> To: [log in to unmask]
> Subject: Re: scale of what?
> Date: 20 February 2000 21:37
> 
> We have seen some interesting suggestions about  measuring the scale of a 
> natural or human made disaster. Are there are physical as well as social 
> dimensions to a disaster, perhaps we need to thing of a composite index, in 
> which the weights would ave to be agreed upon by convention. Thus the 
> inflation index is a weighted index, based on an accepted basket of 
> consumption goods. The UN Human development Index is also a similar index. 
> It has weights for the adequacy of medicare, the prevelance of crime, are 
> pollution, quality of schools, etc.
>          Should we be thinking in terms of a composite index of disasters?
> Mohammed Dore



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