  Vibrations can cause noise in scanning probe microscopies. Relative
vibrations between the scanning sensor and the sample are important but can be
more difficult to determine than absolute vibrations or vibrations relative to
the laboratory. We measure the noise spectral density in a scanning SQUID
microscope as a function of position near a localized source of magnetic field,
and show that we can determine the spectra of all three components of the
relative sensor-sample vibrations. This method is a powerful tool for
diagnosing vibrational noise in scanning microscopies.
