70 Hz Line glitches are strong, monochromatic lines that started appearing in the third observing run (O3) and sit at around 70 Hz. These glitches happened only at LIGO-Livingston during a few days in April 2019. A loud feature at 70 Hz shorter than 0.3 seconds is sometimes accompanied by a fainter one around 60 Hz.
Cause:
Interval shooting of Nikon camera in one of the end stations.