Akutsu-san, thank you for your comment.

I checked the timeseries data (raw one and whitened one) of the other environment sensors such as microphone, accelerometer, voltage meter, by Pastavi.

• On microphones, there were no glitch-like features at the glitch times.
• On all the seismometers, we can see coincident glitches. (see [12/29] and [1/1])
• On voltage sensors (PSL_TABLE, IMCREFL_TABLE, REFL_TABLE, ISS_TABLE), I found the strange transition (up and down).  (see [12/29] and [1/1])
  • When we compare occurred times of glitch on IMMT2 and voltage sensor, the glitch on IMMT2 is earlier.
  • I guess the cause of transition on valtage came from the transition of IFO status, which was reported at [klog#23639]. 
• On one accelerometer, I found the coincident glitches around both time (see [12/29] and [1/1]). The location of accelerometer is around MCF table.
  • This glitch on accelerometer seems coincident with the transition of LSC_LOCK guardian (IFO state).

Order of occurrence

1. seismic motion (frequency is higher than 1Hz)
2. glitch or drift on Type-C suspension
3. (almost same time) interferometer went to Down (LSC_LOCK == Down). The voltage sensor transition happened (up and down). The glitch on accelerometer around MCF table occured