The study of the seismic background noise recorded at the Biryulevo Geophysical Observatory, Joint Institute of Physics of the Earth, Russian Academyof Sciences

Results of the seismic background noise study conducted from 1980 to 1999 i n a 0.005-100-Hz frequency band are presented. A megalopolis is shown to af fect the parameters of seismic noises mainly in a 1- to 5-Hz hand, and thei r level depends appreciably on the hour of day: it reaches 0.3-0.5 mum in t he daytime and decreases by a factor of 4 to 6 in the nighttime. The invest igations conducted from 1997 through 1999 showed that the amplitude-time an d spectral characteristics of the industrial seismic noise coincide with th ose determined from observations made in the 1980s and early 1990s. Present ly, the Biryulevo observatory is the single RAS station at which regular ob servations of the background seismic noise in the vicinity of Moscow are co nducted. The noise level at the observatory is intermediate between those r ecorded at stations located within and beyond the boundaries of Moscow. The results obtained are used for the study of the behavior of small ground mo tion parameters and the interaction between geophysical fields. They can al so be useful for the processing of long-term observation results and for th e development of methods for the seismic noise suppression to improve the a ccuracy of investigations in various fields of science and engineering.