Corey noted the watchdog trip of the BS ISI early Sunday morning.  As he said, this was just a State3 trip where the stage Isolation and Feedforward are blocked but the Damping remains engaged.  Again, this is the normal state of operation for the BS ISI so this trip had no impact on the performance of the platform or the IFO.  A state3 watchdog trip is entered if the motion level returns to okay magnitude within 2 seconds.

Attached is the wave form as seen by the GS13 on the BS.  It looks like it could be an earthquake but I can't be positive as velocities and arrival times between different waves for teleseismic events is not simple.

The candidate Earthquake would appear to be the 4.5Mag event at the far northwest end of the Aleutian Trench.  The low-latency online Earthquake Monitor, does not put the arrival of any  of the EQ wave types at the site at the time of this watchdog trip.  They are all predicted to arrive 10s of minutes before so either this is not an earthquake response or the velocities and distances travelled for this monitor are not correct enough.

Okay--after looking at other platforms (GS13s on other BSC ISIs are inloop,) HEPI L4Cs and the ground STS2, none of which sees this same signal which tripped the BS stage2, nor does any of these see any thing resembling an EQ in the predicted arrival time, I'm going to say this is not a EQ trip of the BS and it possibly came from the platform itself.  More investigation required.

This is all a good thing as we'd be in tough shape if we were vulnerable to a 4.5EQ 5000 km away.