Edit : Neil knows how to make links, now. Tony and Camilla were instrumental in this revelation.

This is an update to my previous post (Neil’s previous post on this topic) about looking for possible explinations why similar seismic wave velocities on-site may or may not knock us out of lock.

The same channels are used in addition to:

SEI- * ARM_GND_BLRMS_30M_100M
SEI- * ARM_GND_BLRMS_100M_300M
Where * is C, D, X, or Y.

I have looked at all earthquake events in O4b, and only ones which knocked us out of lock. This is to simplify the pattern search, for now. Here are the results.

Total events : 29

Events with ISI y-motion dominant : 11 (30-100 Hz) : 8 (100-300 Hz)
Events with ISI x-motion dominant : 3 (30-100 Hz) : 0 (100-300 Hz)
Events with ISI z-motion dominant : 9 (30-100 Hz) : 19 (100-300 Hz)

Events with ISI xy-motion dominant : 1 : 0 (Both axes are similar in amplitude.)
Events with ISI yz-motion dominant : 0 : 1
Events with ISI xz-motion dominant : 0 : 1

Events with IS xyz-motion dominant : 5 : 0

Total SEI- * ARM recorded events : 8
CARM dominant events : 7 : 8
C/XARM dominant events : 1 : 0

Conclusion is that in the 30-100 Hz band, it is equally likely to have either z- or y-axis motion be dominant. In the 100-300 Hz band, the ratio is about 1:2 for z and y motion being dominant during lockloss.

Clearly, common modes are a common (^_^) cause of lockloss.

Note that velocity amplitudes should be explored more.