[time-nuts] OT: NZ Christchurch member
William H. Fite
omniryx at gmail.com
Fri Feb 25 15:51:38 UTC 2011
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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