Seismometer Self-Noise and Measuring Methods

Seismometer self-noise is usually not considered when selecting and using seismic waveform data in scientific research as it is typically assumed that the self-noise is negligibly small compared to seismic signals. However, instrumental noise is part of the noise in any seismic record, and it becomes extremely important to estimate the contribution of instrumental noise to the recordings. In order to estimate the self-noise of a seismometer, it is necessary to remove non-instrumental noise signals (e.g., earthquakes and ambient Earth noise) from the data. This is a general overview on the various methods currently used for estimating the instrument self-noise when using one, two, or three sensors. Variants of these methods, such as rotating horizontal components of Earth motions to maximize the coherence and correcting for misalignments, are also included. Finally, the test setup used for estimating self-noise for the various methods is discussed and examples of corresponding test results are given.