Subtracting tilt from a horizontal-seismometer using a ground-rotation-sensor

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LIGO-P1500278-v3
02 Nov 2016, 13:46

Abstract:: We demonstrate the use of a high-precision ground-rotation-sensor to subtract wind-induced tilt-noise in a horizontal broadband seismometer at frequencies above 10 mHz. The measurement was carried out at the LIGO-Hanford-Observatory using a low-frequency flexure-beam-balance with an autocollimator readout and a T240 seismometer, located in close proximity to each other. Along their common horizontal axis, the two instruments show significant coherence below 100 mHz, which increases as a function of wind speed, likely due to common floor-tilt induced by wind-pressure on the walls of the building and the ground outside. Under wind speeds of 20-30 mph, correcting the seismometer for measured ground-rotation lowered the signal by a factor of ~10 between 10-100 mHz. This paper describes the instruments used, shows representative data for low and high wind-speeds, and discusses the tilt-subtraction and possible limitations.

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LIGO Document P1500278-v4