PSN-L Email List Message

Subject: Re: Lehman construction
From: "Charles R. Patton" crpatton@......
Date: Thu, 13 Jan 2000 13:54:12 -0800

ChrisAtUpw@....... wrote:

>     How has it escaped Mr.Patton's notice that trucks frames are made o=
f a
> lot mild steel, which has a huge magnetic susceptibility cf. oil?

No, obviously the frame is a strong magnetic effect, but the question is
phrased that the oil load made a difference so theoretically all we have =
consider is the delta effect, as the question was, =93=85can you calculat=
e the
capacity of the oil truck?=94  Doug and I are just speculating about othe=
possible effects than just the weight of the oil on the bedrock.  I was
speculating primarily tongue-in-cheek, as probably for any possibility of=
effect to be significant, the Lehman would have to be constructed with th=
magnet on the arm, and we weren=92t given that information.  I haven=92t =
done the
calculations on Doug=92s speculation to know if it=92s too minute to be a=

significant effect or not.  That=92s the fun of the question.

As a side note, there was a paper on the use of the gravitational attract=
method to calibrate some seismometers.  A several kilogram mass was moved=

around a seismometer and the deflection measured to give an actual
sensitivity.  I have the article somewhere in my files.  So that=92s why =
I don=92t
discount Doug=92s speculation as quickly.

Charles R. Patton


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Larry Cochrane <cochrane@..............>