In observational seismology, the long‐period background noise level in horizontal seismometer components is always higher than the vertical component at the same location. It is believed that the horizontal long‐period noise is mostly attributed to ground tilt, yet the authentic tilt recordings of background noise in the seismic frequency band (0.01–20 Hz) have not been recorded successfully. We demonstrate the use of a newly developed optical‐based rotation sensor, blueSeis‐3A, to correct for the tilt effect in a horizontal seismometer. A station with a horizontal long‐period (1 1 s. By subtracting tilt from seismometer records, the horizontal background noise levels could be improved, approximately to the resolution level of the rotation sensors. Our results demonstrate that collocating rotation sensors with seismometers is a feasible way to improve the quality of the long‐period background noise level in seismometer horizontal components when rotation sensors are sufficiently sensitive.
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