English: This image represent a type of glitch appearing in gravitational wave data, nicknamed "koi fish", from data taken by the LIGO Hanford detector in 2015. The top plot represents the output of the detector ("strain") as a function of time, while the bottom plot displays the frequency distribution of the power as a function of time. It should be noted that the data has been whitened to remove much of the noise. This type of glitch is of unknown origin, and covers a broad frequency range, with characteristic "fins" at lower frequencies in the time-frequency plot.