I've added a button the ISI_CONFIG screen that transitions the seismic systems to a robust state to protect the suspensions during a verly large earhquake, like the infamous Montana earthquake or the recent Mexican earthquakes. It's the red button that says Very Large Earthquakes. This script requests the DAMPED state for all of the chambers with ISIs and switches the gains of the all the L4Cs and GS13s. This button is likely temporary, but is probably the state we want to leave the seismic systems in when no-one is on site in the future. The script lives at /opt/rtcds/userapps/release/isi/common/scripts, and is called SET_EQ.py .
As I recall, being the operator on site for the Montana quake, one or two optics/chambers tripped, and I couldn't see any info on a website or even on the plot of our own siesmometers about an EQ, so at first I didn't know that there was an EQ, I thought it could have been some other kind of a failure, and I only knew it was an EQ when more things tripped.
I'm wondering if, given that scenario, you would recommend that in the next observing run Operators transition SEI if any chamber trips, as a precausion for big close EQs?
Would there be enough time for SEIs to transition before a big close EQ arrives?
If not, is there any down side to having an EQ arrive mid-transition?
The motivation for this code comes from the struggles commissioners had during the Mexican earthquake on Sept 8th, this year. The goal is to put the ISIs into a state where it is as easy as possible to keep the ISI damping loops on. It's a last ditch effort to protect the suspensions. So, even if the earthquake is already tripping platforms, it would be best to make the transition, anyway.
For an earthquake as close as the Montana quake, we won't get any advanced notice. I still would not advocate just switching to this configuration just because some chamber tripped. It takes about 45 seconds for a BSC to go from Fully Isolated to damped and about 2 minutes the other way, and there will still be settings to recover after (because the script switches the gains on ISI seismometers). You will also probably have to run an initial alignment. Some thought should be given to a wall FOM for the live ground seismometer signals to help identify if there is an earthquake arriving on site, unannounced. The low frequency blrms on the wall only update every minute, and are probably too slow to help, but all 3 seismometers seeing large, similar signals at the same time is a pretty good indication.