[time-nuts] OT: NZ Christchurch member

[William H. Fite]

For meteorologists and geologists, the Richter scale has a carefully defined
meaning and is used only for purposes where that definition fits.

This per a friend of mine who does seismic stuff for NOAA:
Him:  The Richter number means something very specific to us and something
quite different to the media.  Actually, the Richter doesn't have a great
deal of analytical value to us.  You can say, this is a Category Four
hurricane but that really tells you very little about what is going on in
the storm.  Richter is like that.
Me:  You're saying that the Richter is a poor predictor of surface
disruption?
Him:  Well, obviously a 9 will be expected to do much more damage than a 6
but it is at best a very rough indicator.  The location of the epicenter and
a dozen other factors play into it.
Me:  So how do you assess the damage potential?
Him:  Lots of people think we still rely mainly on the old
pendulum-and-stylus seismographs from the 1930s.  Actually, we take a great
many measurements in addition to seismometry.  But when it comes to
assessing the damage, we go outside and look, just like the TV stations do.

And his final comment:  By the way, did you know that when the shuttle
launches we capture that on virtually every strain guage seismometer in the
country?

I found that interesting.



On Thu, Feb 24, 2011 at 10:56 PM, jimlux <jimlux at earthlink.net> wrote:

> On 2/24/11 5:23 PM, Bob Bownes wrote:
>
>> What is the conversion factor for Richter to dBm? :)
>>
>> Bob
>> As a guy with degrees in geology and EE. I really should know this...:)
>>
>>
>>
> Especially since both are log scales..
>
> The problem is that Richter is log magnitude displacement on a particular
> kind of seismometer (which is sort of a low pass filter) and dBm is log
> power.  However, there should be some sort of scale factor that converts it.
>
> I think it's energy goes as amplitude^1.5.  there's also a scale factor for
> how far the seismograph is from the epicenter.
>
>
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