Item

Abstract

Teleseismic, or distant, earthquakes regularly disrupt the operation of
ground--based gravitational wave detectors such as Advanced LIGO. Here, we
present \emph{EQ mode}, a new global control scheme, consisting of an automated
sequence of optimized control filters that reduces and coordinates the motion
of the seismic isolation platforms during earthquakes. This, in turn,
suppresses the differential motion of the interferometer arms with respect to
one another, resulting in a reduction of DARM signal at frequencies below
100\,mHz. Our method greatly improved the interferometers' capability to remain
operational during earthquakes, with ground velocities up to 3.9\,$\mu
\mbox{m/s}$ rms in the beam direction, setting a new record for both detectors.
This sets a milestone in seismic controls of the Advanced LIGO detectors'
ability to manage high ground motion induced by earthquakes, opening a path for
further robust operation in other extreme environmental conditions.