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Does the vibration due to the earthquakes distort the interference pattern of LIGO's interferometer?

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    $\begingroup$ Yes of course. The whole system must take seismological signals as input so that these can be removed from signals common to both interferometers. Although all possible measures are made to mitigate noise, for an instrument this sensitive total suppression is quite impossible. If a signal is common to both interferometers at the same time, then one knows that it cannot have come from local contamination at either end, so it's a possible candidate. However, it might have come from within the Earth or from a point on the Earth midway between them; seismometers are used to cull .... $\endgroup$ – WetSavannaAnimal Jun 24 '16 at 3:52
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    $\begingroup$ .... these disturbances from the data. Any high correlations left must come from outside the planet. Within these, LIGO looks for those that have the theoretical gravitation wave signatures, e.g. of infalling black hole pairs, but many different templates are used. $\endgroup$ – WetSavannaAnimal Jun 24 '16 at 3:52
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Yes and no. The measurement systems are isolated from ground vibrations by a complex system of supports, but earthquakes will still affect them. There are passive systems which try and isolate the mirrors and active ones which sense local ground movements and cancel them out.

The main defense is the second LIGO in another state which won't feel the same earthquake at the same time. A signal is only likely to be astronomical if it is detected by both of them at (almost) the same time.

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  • $\begingroup$ Interesting. I was under the impression that seismological data were used to rule out disturbances from within the Earth; although I may simply be recalling a draught specification document / feasibility study for the Einstein Telescope here. Do you know for sure whether, once common signals are found, only their resemblance to theoretical templates is used to assess candidates? $\endgroup$ – WetSavannaAnimal Jun 24 '16 at 4:00
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    $\begingroup$ I know that the support system actively measures local ground movements and cancels it out as far as possible, obviously some noise will remain and it is the coincidence of the two sites that is the ultimate safety $\endgroup$ – Martin Beckett Jun 24 '16 at 4:27
  • $\begingroup$ In other words, strong seismic movements are being cleaned from the data set, like one would expect in such an experiment. I think that's much more of a "yes", than a "no". $\endgroup$ – CuriousOne Jun 24 '16 at 7:13
  • $\begingroup$ Yes it would distort them if it wasn't actively damped. No it doesn't affect the result because of the coincidence detection $\endgroup$ – Martin Beckett Jun 24 '16 at 18:34

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