부산대학교 도서관

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 due to floor tilt induced by wind pressure on the walls of the building and the ground outside. Under wind speeds of 10-15 m/s, correcting the seismometer for measured ground rotation lowered the signal by a factor of ∼10, between 10 and 100 mHz. This article describes the instruments used, shows representative data for low and high wind speeds, and discusses the tilt subtraction and possible limitations.