>So here is the challenge question: 

>Assuming identical detector,gain and filtration (they are) and only the
>difference in period, can you calculate the capacity of the oil truck?
>(ST, Give everybody else a day before posting the correct answer,
>please...)

If you going to do the math, you should also calculate whether the drift
is caused by mutual gravitational attraction between the oil truck and
seismometer, as opposed to tilt of the bedrock.

Doug Crice

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