We've been having some confusion in the control room this morning on the IFO alignment as we've been struggling to lock PRMI despite running the usual initial alignment steps successfully and with it having been locked last week. While trending things from last week to see what may have changed, Louis discovered that around 05:45 local time last Monday morning (August 10th), the alignments for the IMs changed notably according to their OSEM readbacks. This lines up with an earthquake that came through at that same time, which tripped the ISI platforms in HAMs 1-5 (noted in the operator shift start alog). It's been seen in the past that a HAM2 ISI trip has caused the IMs to move, so unfortunately this isn't surprising. Also unfortunately, the alignments for the IMs were not restored, so the alignment work that took place later that day to prepare for the peek down the X-arm (alogs 91463 and 91470) would have been done with the assumption the input IFO pointing was good, while in reality it was not.

I have restored the alignments of IMs 1-3 according to their OSEM readbacks before the ISI trip, and Louis confirmed the alignment to the IM4 TRANS and ISS secondloop PDs are good. We will continue to recover alignment in the corner to work towards DRMI locking again.