[time-nuts] OT: NZ Christchurch member

[jimlux]

On 2/25/11 7:55 AM, Poul-Henning Kamp wrote:
> In message<AANLkTikVLp0FMTrm8waFFAD9voHXc8oEo2ZJiCpniQKQ at mail.gmail.com>, "Wil
> liam H. Fite" writes:
>
>> Me:  You're saying that the Richter is a poor predictor of surface
>> disruption?
>
> For damage assement you really need a vector-version of richter,
> vertical does a lot more damage than horizontal on average.
>


Yes.. I doubt anyone still uses the torsion seismometer Richter used, 
although more modern scales (moment magnitude, etc.) still relate back 
(e.g. they set the calibration to match for some notional set of events)..

That way, people have an idea... A Magnitude 3 earthquake within a few 
tens of km of me will be noticeable, if it's quiet. A magnitude 4 will 
be very noticeable, and a 5 will be exciting. A 6 will wake you up in 
the middle of the night.  I'd compare it to something like Mohs 
hardness, except actually with a quantitative basis.  (People who work 
with material properties like hardness use other scales anyway)

It's a "roughly quantitative" measure of energy release, in the same 
sense that kilotons are for explosions. It's like that whole "cup of 
gasoline: dynamite" comparison.. it's the rate of energy (e.g. power) 
that creates the qualitative difference between running my camping stove 
and blasting.

We do the same thing in time-nuttery.. we use log scales to talk about 
performance.. dBc/Hz for phase noise, and really, just the exponent to 
talk about ADEV.  (nobody gets excited about the difference between 
1.1E-13 and 1.5E-13... but the difference between 1E-11 and 1E-15 is 
worth talking about)

Maybe we should start promulgating dBallan?

And maybe get an SI unit... The "Allan", although since the fractional 
frequency error is dimensionless....