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 = to 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= r 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= the effect to be significant, the Lehman would have to be constructed with th= e 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= ion 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. Regards, Charles R. Patton _____________________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>