S Cooper, J Warner
We've been investigating the reasons into why HEPI tripped during O2 to see if anything could be done to prevent it. To do this we've been looking at both the time series sensor data in the local basis (H1,H2,V1,V2 etc), for the IPS, STS, L4C's and Actuators, the saturation counts and the watchdog status for every chamber (BSC's and HAM's - with the exception of HAM1). The first earthquake we ran this on was the Montana earthquake (GPS 118335800) as this was the only earthquake where HEPI was the first to trip.
When we if we look at the saturation counts, we find that only the L4C's are hitting their saturation threshold and are therefore likely causing watchdog trips, the horizontal L4C's are the first to saturate.
If we then compare the levels that the watchdogs trip at across all 10 chambers, we find that ETMX trips at 10% the level of the other chambers. I've attached an annotated PNG highlighting the BSC chambers, and a .fig file that contains the saturation data for all 10 chambers. The dashed lines indicate the watchdog level (multiplied by 10,000 for easier comparison) with the solid lines indicating the specific chambers L4C.
I'm now running the same script for other earthquakes that HEPI tripped in to see if this is an isolated case.
I'm attaching some plots showing the difference between ITMX and ETMX. The first & third subplots are the L4Cs for each chamber, the second and fourth plots are and the watchdogs and number of L4C saturations for each chamber. The L4Cs show roughly the same motion for each chamber (if anything ITMX is worse), but the red traces for the second and fourth plots show that, as Sam found, ETMX is tripping at a much lower number of saturations than ITMX. Actuators and IPS don't saturate for this trip. Hugh, Dave and I have all looked at the models, but haven't found any point where ETMX differs from the other chambers. The saturation threshold is user set, but is the same for all chambers. Not sure what's happening here.
