During the transition to my Day shift, I followed our usual check list for Maintenance days, which included taking SEI_CONF to SC_OFF_NOBRSXY. When Hugh and I went to recenter the STSs and T240, the SEI_ENV node was still looking for earthquakes and saw large ground motion, caused by Hugh and I. The node proceeded to switch to earthquake mode in the middle of our recentering. Many chambers tripped as a result.

The failure here was that I was following a checklist that I had not updated to reflect this new SEI_ENV node. This node should be taken to the MAINTENANCE state every Tuesday morning to avoid this in the future. I will update the checklist now, and double check others to make sure it doesn't need to be somewhere else that I can't think of.