- Earthquakes provide an impulse-type excitation that is potentially useful to characterize seismic isolation overall of current ground-based gravitational-wave detectors. We report on a broadband seven-minute descending chirp (< 700 Hz) in LIGO-H1 in response to an M4.1 earthquake at 15km WNW of Belfair, WA, of February 23 2017 in LIGO O2. This event EQ170223, picked up 80s posterior to the earthquake, is entirely consistent with the event rate of about one event >M4 in the Hanford area over the total duration of four months of joint H1 and L1 data during O2. A quasi-periodic modulation of about 40mHz shows a complex detector response, the origin of which appears to involve more than suspension of mirrors alone. Gathering events over a few years will facilitate a detailed map of the performance of seismic isolation as a whole as a function of earthquake magnitude and direction. An brief outlook on KAGRA is included, whose exposure to strong earthquakes is considerably more severe. This unique signal may also serve as a novel signal injection challenge for un-modeled searches of broadband extended gravitational-wave emission of extreme transient events in the Local Universe.
- van Putten, Levinson, Frontera, Guidorzi, Amati, & Della Valle, 2019, EJP Plus, to appear
van Putten, Della Valle & Levinson, 2019, ApJ, 876, L2
van Putten & Della Valle, 2019, MNRAS, 482, L46
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