During one of the large eqs over the weekend all of the BSC-ISI tripped. I checked one of the chambers and the trip was due to large low frequency drive railing the stage 2 horizontal actuators. The earthquake was big enough SEI_ENV went LARGE_EQ, well after the IFO lost lock, but also after the ISIs started tripping. In SEI_ENV I've reduced the threshold on the peak mon to 6000, about 1.5x the largest eq we've ever ridden out, down from 10000. I've also changed the stage 2 blends used in this state to some 1.5hz blends which roll-off the gs13s at low frequency much more aggressively. I don't think these changes would have been enough to prevent the ISI trips for this particular earthquake, the ISIs started tripping while peak mon was around 4000, so there must have been a large amount of ground motion that was out of band for that channel.