Low-Frequency Noise at BFO

To estimate noise levels at a station is always somewhat subjective since naturally occurring noise processes are not stationary. Hence any estimate will depend un the selected segment of data. I have chosen to blindly rely on order statistics and to represent station noise levels by the median psd levels. Thus 50 percent of the time noise levels at BFO are lower than indicated by the median.

G. Ekström at the Harvard Waveform Quality Center continuously estimates noise levels at all the stations of the Global Seismic Network (GSN) and he uses the 10 percent quantile to represent the noise levels at a given station. This means that 10 percent of the time noise levels are lower than given by Ekströms estimate.

The evolution of vertical seismic noise levels at GSN stations ( including BFO/II ) is summarized here.