A Study of Seismic Noise Level at the KNET Stations

摘要

We estimated the level of seismic noise for stations of the KyrgyzNetwork (KNET) for 19 years of its operation (1999-2017) in real time. For each channel of a seismic station (east-west, north-south, vertical) we selected fifteen-minute segments of 100-Hz seismic noise distributed over all seasons of the year (March, June, September, and December) and several times of the day (0, 6, 12, and 18 h UTC). We calculated power spectral densities of seismic noise and found the probability density of signal power spectral density for all selected frequencies/periods. The resulting distributions were compared with Peterson's seismic noise models (Peterson, 1993). The maximum absence of stochastic noise occurred at 00 and 18 h UTC for all KNET stations. The level of seismic noise is little affected by the seasons at periods of 2-5 s, slightly lowering in the summer and increasing in the cold seasons at periods of 5-10 s. September is the less favorable for periods of 0.02-2 s. The stations as a whole possess good characteristics at periods of 0.02-10 s (frequencies of 0.1-50 Hz) and can well be said to be noiseless.