JeffB reported IFO Lockloss Thursday from 6.2 EQ near Japan.

Based on the timing and the cavity build up, it looks like the vertical P wave is the strongest candidate for the lock loss.  This is a pretty big EQ and only ~4400 miles distance.  At  this distance, the P-Wave travel time is maybe 12 minutes and the S(shear)-wave TT is about 20 minutes.

The two attached plots shows a transmitted light sum and the CS ground seismometers.  This is a very nice example of classical earthquake ground motion with distinct arrivals of the P, S, and surface waves.  The second attachment has the transmitted light sum overlain on the seismos.  The vertical correlates well and shows a stronger signal although the X signal on the seismo also shows color at the loss time.  This makes sense as the P-Wave is arriving from depth (Z) and the great circle route is very much from the NW direction(X).

This is news as we were thinking our EQ LLs were primarily from surface and shear waves.  I still think that is mostly true but closer larger EQs may be P-Wave problems.