Statistical characteristics and stationarity properties of low-frequency seismic signals

Statistical properties of microseismic signals are studied in the frequency range 0.03–15 Hz at various points of the Earth near and far from sources of microseisms. It is found that various frequency ranges differ in the property of stationarity. The minimum interval of stationarity of microseisms in the range 0.12–1.1 Hz is estimated at 1–1.5 h. A conclusion is drawn that the measurement accuracy of the spectral density of microseisms cannot be improved above a certain limit by increasing the time of signal stacking.