Hello. I’ve read in the online manual that the Geophone should ideally be no more than just a few degrees off from being level. But I cannot find any info about the accelerographs on the Shake board. (This is assuming I am not housing all of the components in the case). Since the accelerographs cover the x, y, and z directions, can the shake board be tilted and can the effects of tilt be measured and removed during processing?
Hello ded1,
yes, the board with the accelerometers has to be leveled like the units with geophones.
You could try to remove the tilt effect in post-processing, but the instrument responses would change, and it would be very hard to change that. So, it’s better to place them well leveled on their supports.
hi,
if, in the case where it is not possible to level the unit, in order to make sure each meter is oriented to gravity and North as expected, it would be possible to post-process the data to convert it back to the expected values since the meters themselves remain orthogonally oriented to each other no matter how the unit is oriented itself.
however, in order to do this, you would also need to know the exact orientation vs. gravity and North (i.e., “down”, and “magnetic north”) of the three meters when the recording took place. and, depending on the medium the unit is sitting on top of, if you can’t guarantee that the unit will not move (or re-orient itself) over time, then returning the data back to X-Y-Z coordinates vs. gravity and North would be very difficult indeed.
assuming you do know the unit’s orientation vs. gravity and North, and that it remains fixed, there are trig functions which could do this conversion for you, but this is definitely beyond the scope of this forum.
i would refer you to articles in the seismic literature which address this to see if there is a solution available for your specific use-case.
hope this helps,
richard
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