Margin Seismology
Figure 6.
The broadband velocity background noise amplitude spectra (taken from data immediately preceding the teleseism) indicates that the Z- and E-components are responding normally and recording the seismic background noise (they both record the microseismic peak at ~0.2 Hz) while the N-component (lower trace) is not recording the background noise. The N-component  amplitude spectra also has several high-amplitude narrow-band peaks at frequencies above ~0.5 Hz.  Since the N-component recorded the teleseism but not the local earthquake, it is apparent that the  sensor is alive but operating at reduced sensitivity. This is most likely due to its mass position being well off center. This was corrected by manually recentering via the ROV connection on the April 22 dive.

Oct. 07, 2009 East component mass position